Random results with random access query
Hi,
when I execute a random access query
(fetchConfig.setResultSetType(ResultSet.TYPE_SCROLL_INSENSITIVE);
fetchConfig.setFetchDirection(ResultSet.FETCH_UNKNOWN)) and iterate over the
result set twice, the second time the objects are retrieved in a different
order, also when I set the ordering of the objects. This only happens if the
first loop touches the last item. If not, everything works fine. I am using
MS Sql Server, microsoft driver, kodo 3.4
regards,
Christiaan
Hi,
I am using datastore identity. I do implement equals and hashcode in the
super class, not sure whether that is of any impact. The order of the items
look random to me, however it stays constant after the second loop. The same
order is also produced when I re-start the test application. The output
shows the index of the object I am retrieving, the description of the object
(which is also the order in which the items are created) and their order
attribute. The query sorts on the order attribute. As you can see the first
loop is correct. I now and then have the situation where the last item in
the first loop (retrieve 7) results in the first item (item nr 0) being
retrieved. Same behaviour applies for both jtds and microsoft driver.
first loop:
retrieve 0: item nr: 0 order: 0
retrieve 1: item nr: 1 order: 1
retrieve 2: item nr: 2 order: 2
retrieve 3: item nr: 3 order: 3
retrieve 4: item nr: 4 order: 4
retrieve 5: item nr: 5 order: 5
retrieve 6: item nr: 6 order: 6
retrieve 7: item nr: 7 order: 7
second loop
retrieve 0: item nr: 3 order: 3
retrieve 1: item nr: 6 order: 6
retrieve 2: item nr: 7 order: 7
retrieve 3: item nr: 0 order: 0
retrieve 4: item nr: 5 order: 5
retrieve 5: item nr: 4 order: 4
retrieve 6: item nr: 2 order: 2
retrieve 7: item nr: 1 order: 1
third loop
retrieve 0: item nr: 3 order: 3
retrieve 1: item nr: 6 order: 6
retrieve 2: item nr: 7 order: 7
retrieve 3: item nr: 0 order: 0
retrieve 4: item nr: 5 order: 5
retrieve 5: item nr: 4 order: 4
retrieve 6: item nr: 2 order: 2
retrieve 7: item nr: 1 order: 1
"Marc Prud'hommeaux" <[email protected]> wrote in message
news:[email protected]...
Christiaan-
My first guess is are you using application identity, and if so, are you
correctly implementing the equals() and hashCode() method? Failure to do
so may conceivably cause this problem.
Otherwise, can you provide some details about how the results are our of
order? It it exactly reverse or something, or are elements in random
order?
Christiaan wrote:
Hi,
when I execute a random access query
(fetchConfig.setResultSetType(ResultSet.TYPE_SCROLL_INSENSITIVE);
fetchConfig.setFetchDirection(ResultSet.FETCH_UNKNOWN)) and iterate over
the result set twice, the second time the objects are retrieved in a
different order, also when I set the ordering of the objects. This only
happens if the first loop touches the last item. If not, everything works
fine. I am using MS Sql Server, microsoft driver, kodo 3.4
regards,
Christiaan
Marc Prud'hommeaux
SolarMetric Inc.
Similar Messages
-
Can I produce such a result with a single query?
I am having a table with records like
A....B
1....20
2....19
3....03
4....09
5....74
6....24
7....31
Column A is a primary key and Column B has radomly generated positive integer numbers. I need to generate one more column C with randomly generated positive integer values (including 0) so that -
1) The values genereated for the Column C must be less than or equal to corresponding value of Column B.
2). The randomly generated values for Column C should be in such a way so that the sum of values for Column C would be 30% of the sum of values of Column B.
In our example, the sum(B) = 180. So the sum(C) should be around 54.
One of the snap of column C can be like this...
A....B....C
1....20....14
2....19....00
3....03....02
4....09....03
5....74....03
6....24....01
7....31....31
......==-..==
.....180...54
How do I write a query to produce such a result?You may try the following:
SQL> CREATE TABLE t AS SELECT ROWNUM a,ROUND(DBMS_RANDOM.VALUE(10,99)) b FROM user_objects WHERE ROWNUM <= 15
Table created.
SQL> BREAK on l
SQL> COMPUTE SUM OF b on l
SQL> COMPUTE SUM OF c on l
SQL> SELECT a,
b,
c,
l
FROM (SELECT a,
b,
c,
ROUND (30 / 100 * s) s,
SUM (c) OVER (PARTITION BY l) d,
l
FROM (SELECT a,
b,
l,
ROUND (DBMS_RANDOM.VALUE (1, b)) c,
SUM (b) OVER (PARTITION BY l) s
FROM t,
(SELECT LEVEL l
FROM DUAL
CONNECT BY LEVEL <= 50000)))
WHERE d = s
A B C L
1 12 3 184
2 40 31
3 79 7
4 46 8
5 18 7
6 14 3
7 48 12
8 32 8
9 67 16
10 25 20
11 23 17
12 22 2
13 24 8
14 74 5
15 48 25
572 172 sum
1 12 3 10298
2 40 25
3 79 32
4 46 6
5 18 6
6 14 4
7 48 4
8 32 26
9 67 31
10 25 2
11 23 3
12 22 12
13 24 7
14 74 3
15 48 8
572 172 sum
1 12 8 13450
2 40 5
3 79 12
4 46 13
5 18 11
6 14 11
7 48 8
8 32 22
9 67 3
10 25 4
11 23 2
12 22 14
13 24 12
14 74 40
15 48 7
572 172 sum
1 12 1 16656
2 40 31
3 79 3
4 46 20
5 18 9
6 14 5
7 48 18
8 32 24
9 67 16
10 25 5
11 23 7
12 22 2
13 24 6
14 74 23
15 48 2
572 172 sum
1 12 5 19842
2 40 11
3 79 11
4 46 12
5 18 2
6 14 2
7 48 3
8 32 16
9 67 10
10 25 11
11 23 17
12 22 18
13 24 6
14 74 26
15 48 22
572 172 sum
1 12 3 22337
2 40 18
3 79 9
4 46 26
5 18 11
6 14 9
7 48 25
8 32 14
9 67 6
10 25 3
11 23 21
12 22 12
13 24 10
14 74 4
15 48 1
572 172 sum
1 12 5 24501
2 40 11
3 79 48
4 46 3
5 18 6
6 14 8
7 48 2
8 32 3
9 67 21
10 25 7
11 23 16
12 22 2
13 24 16
14 74 12
15 48 12
572 172 sum
1 12 8 24555
2 40 29
3 79 7
4 46 13
5 18 5
6 14 4
7 48 20
8 32 3
9 67 17
10 25 13
11 23 18
12 22 2
13 24 5
14 74 27
15 48 1
572 172 sum
1 12 7 27312
2 40 11
3 79 3
4 46 37
5 18 3
6 14 7
7 48 16
8 32 8
9 67 27
10 25 2
11 23 14
12 22 4
13 24 20
14 74 9
15 48 4
572 172 sum
1 12 3 29197
2 40 12
3 79 24
4 46 17
5 18 6
6 14 9
7 48 17
8 32 17
9 67 4
10 25 23
11 23 15
12 22 4
13 24 5
14 74 2
15 48 14
572 172 sum
1 12 8 32635
2 40 5
3 79 21
4 46 1
5 18 9
6 14 6
7 48 20
8 32 6
9 67 43
10 25 10
11 23 15
12 22 5
13 24 4
14 74 15
15 48 4
572 172 sum
1 12 2 38404
2 40 26
3 79 6
4 46 28
5 18 4
6 14 2
7 48 4
8 32 13
9 67 19
10 25 3
11 23 3
12 22 11
13 24 13
14 74 32
15 48 6
572 172 sum
1 12 10 38830
2 40 5
3 79 8
4 46 3
5 18 2
6 14 12
7 48 42
8 32 5
9 67 27
10 25 4
11 23 9
12 22 11
13 24 11
14 74 10
15 48 13
572 172 sum
1 12 2 42291
2 40 5
3 79 34
4 46 24
5 18 15
6 14 7
7 48 7
8 32 10
9 67 1
10 25 5
11 23 20
12 22 8
13 24 3
14 74 7
15 48 24
572 172 sum
1 12 5 47614
2 40 6
3 79 15
4 46 32
5 18 6
6 14 12
7 48 8
8 32 7
9 67 6
10 25 22
11 23 8
12 22 3
13 24 17
14 74 13
15 48 12
572 172 sum
225 rows selected. -
How can I share the results with limited access to another user
I am adding another user to be able to see results of forms submitted, I want the user to add some text into the results view but I don't want him to have access the the design view. How can I make that happen?
Karina Wiggs
Director of Operations
Community Lodgings
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On Thu, Dec 4, 2014 at 11:43 AM, Vikrantt Singh <[email protected]> -
Getting result with single query
Hi,
I'm using db 10.2.0.1.0
I have a table emp_shift , with data like below
EmpCode Shift Effdate Default
1 SHFT1 02-jan-2012 N
1 SHFT2 04-jan-2012 Y
1 SHFT3 04-jan-2012 NSo if user inputs EmpCode and Effdate, based on that i've to take the latest record, with default = 'Y' (if any) else default 'N'
Suppose
Case 1 : Input Empcode:1 Date:10-jan-2012
Then i should get the below record
1 SHFT2 04-jan-2012 YCase 2 : Input Empcode:1 Date:03-jan-2012
Then i should get the below record
1 SHFT1 02-jan-2012 NI want this result with a single query, is this possible?
Thanks
DivyaHi Thank you both,
I'm trying this process through forms. and my forms version is 6i.
There where i'm trying the query with the cursor, i'm getting error
Encountered the symbol Order when expecting one of the following
.()...and my cursor is
Cursor cur_shft(vemp Varchar2,vdate Varchar2) is Select ESM_SHIFT_TYPE
from (Select ESM_SHIFT_TYPE from EMPLOYEE_SHIFT_MASTER
Where ESM_EMP_CODE = vemp
and ESM_EFF_DATE <= vdate
Order by ESM_EFF_DATE desc,Esm_Default desc)
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Uncached Write 120.10 67.95 MB/sec [256K blocks]
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byte[] sss = new byte[2462];
int j j = vansfile.read(sss)
now i know roughly at which offsets some data fields are kept, for instance bytes
sss[0] and sss[1] = a label which is stored in ascii,and bytes 7 to 27 hold a persons name ie byte 7 holds 78 = N byte 8 holds 65 = A ... which ends up spelling NATASHA (the persons name). SO FAR SO GOOD
NOW apparently bytes 1413 to 1420 holds a monetary value (which i assume is encoded as an integer or a double). if i print the byte values, i get the following where the number before the : is the byte and the number after the : is the value.
1413 : -102
1414 : -103
1415 : -103
1416 : -103
1417 : -103
1418 : -7
1419 : -126
1420 : 64
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and it has the value 607.2
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If you use the longBitsToDoublemethod, it needs a long as its argument. The easiest way to do that is to create a long using the hex values of the bytes. For example, using your data converted to hex:
1420: 40
1419: 82
1418: f9
1417: 99
1416: 99
1415: 99
1414: 99
1413: 9a
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Hi,
When we say that the ArrayList is random access,what exactly do we mean by "Random Access"I was half tempted to start my post out with sigh like some of the regulars around here, but then I realized how annoying and stupid that is...
Anyway, have you tried googling 'random access'? When I did, the fourth result was a fairly decent description of what random access means.
From http://www.webopedia.com/TERM/R/random_access.html
Refers to the ability to access data at random. The opposite of random access is sequential access. To go from point A to point Z in a sequential-access system, you must pass through all intervening points. In a random-access system, you can jump directly to point Z. Disks are random access media, whereas tapes are sequential access media.
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Why do I need to define these in std for my random access iterator???
Hi guys,
I have written my own iterator class, to support 1-d slices of 2-d matrices, 2-d slices of 3-d matrices, etc.
At first I wrote the class as a bidirectional iterator, but then I needed to extend it to random access so that I could pass these iterators to std::sort etc. No problem, I thought, I just needed to add friend operators for "iterator-iterator" and "iterator+/-distance".
So, I did that and tested the code with VS6 and various versions of g++, with no problems. Isn't STL great!
But I had endless problems with Studio 10. It kept griping that various mostly-internal-looking template functions were not defined. The only way I could get it to work was to define these:
#if (defined __SUNPRO_CC) && (__SUNPRO_CC <= 0x570)
namespace std
template<typename T> // Sigh
typename matrixit<T>::
difference_type distance(const matrixit<T>& a, const matrixit<T>& b) {
return b-a;
template<typename T> // WTF?
T* __value_type(const matrixit<T>&) {
return static_cast<T*>(0);
template<typename T> // WTF?
typename matrixit<T>::
difference_type* __distance_type(const matrixit<T>&) {
return static_cast<typename matrixit<T>::difference_type*>(0);
template<typename T> // WTF?
typename matrixit<T>::
iterator_category __iterator_category(const matrixit<T>&) {
return typename matrixit<T>::iterator_category();
#endif
Why do I have to do this, or am I missing something in my iterator class (eg, typedefs), or do I need to derive it from something? Here is what it looks like:
template<typename T>
class matrixit
public:
typedef T& reference;
typedef T* pointer;
typedef T value_type;
typedef size_t size_type;
typedef ptrdiff_t difference_type;
typedef std::random_access_iterator_tag iterator_category;
Ta, Simon.Come on, it is not that hard to work around the limitations of Cstd. For what you show here, you can use:
namespace std {
template <class Iterator> struct iterator_traits
typedef typename Iterator::value_type value_type;
typedef typename Iterator::difference_type difference_type;
typedef typename Iterator::pointer pointer;
typedef typename Iterator::reference reference;
typedef typename Iterator::iterator_category iterator_category;
template <class T> struct iterator_traits<T*>
typedef T value_type;
typedef ptrdiff_t difference_type;
typedef T* pointer;
typedef T& reference;
typedef random_access_iterator_tag iterator_category;
template <class T> struct iterator_traits<const T*>
typedef T value_type;
typedef ptrdiff_t difference_type;
typedef const T* pointer;
typedef const T& reference;
typedef random_access_iterator_tag iterator_category;
template <class ForwardIterator>
inline ptrdiff_t
distance (ForwardIterator first, ForwardIterator last)
ptrdiff_t n = 0;
__distance(first, last, n,
iterator_traits<ForwardIterator>::iterator_category());
return n;
template <class InputIterator, class T>
inline typename iterator_traits<InputIterator>::difference_type
count (InputIterator first, InputIterator last, const T& value)
typename iterator_traits<InputIterator>::difference_type result;
count(first,last,value,result);
return result;
template <class InputIterator, class Predicate>
inline typename iterator_traits<InputIterator>::difference_type
count_if (InputIterator first, InputIterator last, Predicate pred)
typename iterator_traits<InputIterator>::difference_type result;
count_if(first,last,pred,result);
return result;
template < class T >
inline typename T::value_type*
__value_type (const T&)
{ return (typename T::value_type*)(0); }
template < class T >
inline typename T::difference_type*
__distance_type(const T&)
{ return (typename T::difference_type*)(0); }
template < class T >
inline typename T::iterator_category
__iterator_category (const T&)
typename T::iterator_category tmp;
return tmp;
} // namespace std
For the missing constructor of vector with iterators, you can simply use std::copy with a back_insert_iterator.
The hardest thing to work around is probably the missing conversion between std::pair of various types (for instance with various constness when you use std::map), but it can still be handled by always specifying the type of the pair instead of relying on std::make_pair.
And if there is a thing you really don't know how to work around, you can always ask here... -
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In other words, I could see:
A. Cluster-shared VHDXs are accessed (more-or-less) based on the type of data they're used for
B. All cluster-shared VHDXs are (more-or-less) accessed sequentially
C. All cluster-shared VHDXs are (more-or-less) accessed randomly.
I have one source that says that for a relatively simple SMB setup like we have that "C" is the recommendation. I'm curious if anyone else has run into this or seen an official best-practice...?Is there a best practice on the SAN optimization of LUNs for CSV VHDX files - e.g. sequential vs. random access?
We recently set up a small two-node Hyper-V 2012 R2 Failover Cluster. As I was creating LUNs for the CSV vhdx files, our SAN (like most, I think) has some pre-set optimization options which are more or less sequential vs. random access. There's now the abstraction
layer of shared VHDX files and the actual data those VHDXs are being used to store. Are there any best-practices for SAN optimization in this regard?
In other words, I could see:
A. Cluster-shared VHDXs are accessed (more-or-less) based on the type of data they're used for
B. All cluster-shared VHDXs are (more-or-less) accessed sequentially
C. All cluster-shared VHDXs are (more-or-less) accessed randomly.
I have one source that says that for a relatively simple SMB setup like we have that "C" is the recommendation. I'm curious if anyone else has run into this or seen an official best-practice...?
There as good article published recently by Jose Barreto about CSV performance counters. See:
Cluster Shared Volume: Performance Counters
http://blogs.msdn.com/b/clustering/archive/2014/06/05/10531462.aspx
You can run DiskSPD or Intel I/O Meter yourself to see what workload you'll get @ CSV with 10+ VMs doing different I/O types. We did and you'll get
4-8KB 100% random reads and writes (just make sure you gather statistics for a long time).
So that's type of workload you could optimize your LUN @ SAN level.
StarWind Virtual SAN clusters Hyper-V without SAS, Fibre Channel, SMB 3.0 or iSCSI, uses Ethernet to mirror internally mounted SATA disks between hosts. -
This program is supposed to retrieve data from TelephoneUI's JTextFields, store the data in a RandomAccessRecord class object record and call the write method of class RandomAccessRecord to output the data.
Two questions
Is there any way to check if the data was actually written to the file without writing a new class to read the file?
How can I make it so that the file-position pointer for object output start from byte 0 for the first record and move 94 bytes after each read? Right now the file-position pointer moves 94 bytes after each read but starts from 94.
public class WriteRandomFile extends JFrame {
private RandomAccessFile output;
private TelephoneUI userInterface;
private JButton enterButton, openButton;
// set up GUI
public WriteRandomFile()
super( "Write to random access file" );
// create instance of reusable user interface TelephoneUI
userInterface = new TelephoneUI(4); // four textfields
getContentPane().add( userInterface,
BorderLayout.CENTER );
// get reference to generic task button doTask1 in TelephoneUI
openButton = userInterface.getDoTask1Button();
openButton.setText( "Open..." );
// register listener to call openFile when button pressed
openButton.addActionListener(
// anonymous inner class to handle openButton event
new ActionListener() {
// allow user to select file to open
public void actionPerformed( ActionEvent event )
openFile();
} // end anonymous inner class
); // end call to addActionListener
// register window listener for window closing event
addWindowListener(
// anonymous inner class to handle windowClosing event
new WindowAdapter() {
// add record in TelephoneUI, then close file
public void windowClosing( WindowEvent event )
if ( output != null )
addRecord();
closeFile();
} // end anonymous inner class
); // end call to addWindowListener
// get reference to generic task button doTask2 in TelephoneUI
enterButton = userInterface.getDoTask2Button();
enterButton.setText( "Enter" );
enterButton.setEnabled( false );
// register listener to call addRecord when button pressed
enterButton.addActionListener(
// anonymous inner class to handle enterButton event
new ActionListener() {
// add record to file
public void actionPerformed( ActionEvent event )
addRecord();
} // end anonymous inner class
); // end call to addActionListener
setSize( 300, 150 );
show();
// enable user to choose file to open
private void openFile()
// display file dialog so user can select file
JFileChooser fileChooser = new JFileChooser();
fileChooser.setFileSelectionMode(
JFileChooser.FILES_ONLY );
int result = fileChooser.showOpenDialog( this );
// if user clicked Cancel button on dialog, return
if ( result == JFileChooser.CANCEL_OPTION )
return;
// obtain selected file
File fileName = fileChooser.getSelectedFile();
// display error if file name invalid
if ( fileName == null ||
fileName.getName().equals( "" ) )
JOptionPane.showMessageDialog( this,
"Invalid File Name", "Invalid File Name",
JOptionPane.ERROR_MESSAGE );
else {
// open file
try {
output = new RandomAccessFile( fileName, "rw" );
enterButton.setEnabled( true );
openButton.setEnabled( false );
// process exception while opening file
catch ( IOException ioException ) {
JOptionPane.showMessageDialog( this,
"File does not exist",
"Invalid File Name",
JOptionPane.ERROR_MESSAGE );
} // end method openFile
// close file and terminate application
private void closeFile()
// close file and exit
try {
if ( output != null )
output.close();
System.exit( 0 );
// process exception while closing file
catch( IOException ioException ) {
JOptionPane.showMessageDialog( this,
"Error closing file",
"Error", JOptionPane.ERROR_MESSAGE );
System.exit( 1 );
// add one record to file
public void addRecord()
String fields[] = userInterface.getFieldValues();
RandomAccessRecord record =
new RandomAccessRecord();
int count = 1;
// ensure field has a value
if ( ! fields[ TelephoneUI.LASTNAME ].equals( "" ) ) {
// output values to file
try {
record.setFirstName( fields[ TelephoneUI.FIRSTNAME ] );
record.setLastName( fields[ TelephoneUI.LASTNAME ] );
record.setAddress( fields[ TelephoneUI.ADDRESS ] );
record.setPhone( Integer.parseInt( fields[ TelephoneUI.PHONENUMBER ] ) );
count = count * 94;
output.seek( count );
record.write( output );
userInterface.clearFields(); // clear TextFields
// process improper account number or balance format
catch ( NumberFormatException formatException ) {
JOptionPane.showMessageDialog( this,
"Bad account number or balance",
"Invalid Number Format",
JOptionPane.ERROR_MESSAGE );
// process exceptions while writing to file
catch ( IOException ioException ) {
closeFile();
} // end method addRecord
// execute application
public static void main( String args[] )
new WriteRandomFile();
} // end class WriteRandomFileThis program is supposed to retrieve data from
TelephoneUI's JTextFields, store the data in a
RandomAccessRecord class object record and call the
write method of class RandomAccessRecord to output
the data.
Two questions
Is there any way to check if the data was actually
written to the file without writing a new class to
read the file? Why? If the io operations are not working (and not throwing exceptions) then you might as well give up.
>
How can I make it so that the file-position pointer
for object output start from byte 0 for the first
record and move 94 bytes after each read? Right now
the file-position pointer moves 94 bytes after each
read but starts from 94.Huh? It moves 94 and you want it to move 94?
Perhaps you are just looking for the getFilePointer() and seek() methods?
>
public class WriteRandomFile extends JFrame {
private RandomAccessFile output;
private TelephoneUI userInterface;
private JButton enterButton, openButton;
// set up GUI
public WriteRandomFile()
super( "Write to random access file" );
// create instance of reusable user interface
erface TelephoneUI
userInterface = new TelephoneUI(4); // four
/ four textfields
getContentPane().add( userInterface,
BorderLayout.CENTER );
// get reference to generic task button doTask1
oTask1 in TelephoneUI
openButton = userInterface.getDoTask1Button();
openButton.setText( "Open..." );
// register listener to call openFile when
e when button pressed
openButton.addActionListener(
// anonymous inner class to handle
to handle openButton event
new ActionListener() {
// allow user to select file to open
public void actionPerformed( ActionEvent
ActionEvent event )
openFile();
} // end anonymous inner class
); // end call to addActionListener
// register window listener for window closing
losing event
addWindowListener(
// anonymous inner class to handle
to handle windowClosing event
new WindowAdapter() {
// add record in TelephoneUI, then close
, then close file
public void windowClosing( WindowEvent
WindowEvent event )
if ( output != null )
addRecord();
closeFile();
} // end anonymous inner class
); // end call to addWindowListener
// get reference to generic task button doTask2
oTask2 in TelephoneUI
enterButton =
tton = userInterface.getDoTask2Button();
enterButton.setText( "Enter" );
enterButton.setEnabled( false );
// register listener to call addRecord when
d when button pressed
enterButton.addActionListener(
// anonymous inner class to handle
to handle enterButton event
new ActionListener() {
// add record to file
public void actionPerformed( ActionEvent
ActionEvent event )
addRecord();
} // end anonymous inner class
); // end call to addActionListener
setSize( 300, 150 );
show();
// enable user to choose file to open
private void openFile()
// display file dialog so user can select file
JFileChooser fileChooser = new JFileChooser();
fileChooser.setFileSelectionMode(
JFileChooser.FILES_ONLY );
int result = fileChooser.showOpenDialog( this
( this );
// if user clicked Cancel button on dialog,
ialog, return
if ( result == JFileChooser.CANCEL_OPTION )
return;
// obtain selected file
File fileName = fileChooser.getSelectedFile();
// display error if file name invalid
if ( fileName == null ||
fileName.getName().equals( "" ) )
JOptionPane.showMessageDialog( this,
"Invalid File Name", "Invalid File
Invalid File Name",
JOptionPane.ERROR_MESSAGE );
else {
// open file
try {
output = new RandomAccessFile( fileName,
e( fileName, "rw" );
enterButton.setEnabled( true );
openButton.setEnabled( false );
// process exception while opening file
catch ( IOException ioException ) {
JOptionPane.showMessageDialog( this,
"File does not exist",
"Invalid File Name",
JOptionPane.ERROR_MESSAGE );
} // end method openFile
// close file and terminate application
private void closeFile()
// close file and exit
try {
if ( output != null )
output.close();
System.exit( 0 );
// process exception while closing file
catch( IOException ioException ) {
JOptionPane.showMessageDialog( this,
"Error closing file",
"Error", JOptionPane.ERROR_MESSAGE );
System.exit( 1 );
// add one record to file
public void addRecord()
String fields[] =
ds[] = userInterface.getFieldValues();
RandomAccessRecord record =
new RandomAccessRecord();
int count = 1;
// ensure field has a value
if ( ! fields[ TelephoneUI.LASTNAME ].equals(
quals( "" ) ) {
// output values to file
try {
record.setFirstName( fields[
stName( fields[ TelephoneUI.FIRSTNAME ] );
record.setLastName( fields[
stName( fields[ TelephoneUI.LASTNAME ] );
record.setAddress( fields[
ddress( fields[ TelephoneUI.ADDRESS ] );
record.setPhone( Integer.parseInt(
teger.parseInt( fields[ TelephoneUI.PHONENUMBER ] )
count = count * 94;
output.seek( count );
record.write( output );
userInterface.clearFields(); // clear
); // clear TextFields
// process improper account number or
number or balance format
catch ( NumberFormatException
Exception formatException ) {
JOptionPane.showMessageDialog( this,
"Bad account number or balance",
"Invalid Number Format",
JOptionPane.ERROR_MESSAGE );
// process exceptions while writing to file
catch ( IOException ioException ) {
closeFile();
} // end method addRecord
// execute application
public static void main( String args[] )
new WriteRandomFile();
} // end class WriteRandomFile -
Modify Record Number in a Random Access File
Hi Does anyone know if I can modify the record number in the random access file hardware.dat for each hardware record each time and update it in hardware.dat to display it? Also why does it say "Record does not exist" if I modify the record number for a hardware and try to update it but could not find that record?
Here is the code below:
// Exercise 14.11: HardwareRecord.java
package org.egan; // packaged for reuse
public class HardwareRecord
private int recordNumber;
private String toolName;
private int quantity;
private double cost;
// no-argument constructor calls other constructor with default values
public HardwareRecord()
this(0,"",0,0.0); // call four-argument constructor
} // end no-argument HardwareRecord constructor
// initialize a record
public HardwareRecord(int number, String tool, int amount, double price)
setRecordNumber(number);
setToolName(tool);
setQuantity(amount);
setCost(price);
} // end four-argument HardwareRecord constructor
// set record number
public void setRecordNumber(int number)
recordNumber = number;
} // end method setRecordNumber
// get record number
public int getRecordNumber()
return recordNumber;
} // end method getRecordNumber
// set tool name
public void setToolName(String tool)
toolName = tool;
} // end method setToolName
// get tool name
public String getToolName()
return toolName;
} // end method getToolName
// set quantity
public void setQuantity(int amount)
quantity = amount;
} // end method setQuantity
// get quantity
public int getQuantity()
return quantity;
} // end method getQuantity
// set cost
public void setCost(double price)
cost = price;
} // end method setCost
// get cost
public double getCost()
return cost;
} // end method getCost
} // end class HardwareRecord-------------------------------------------------------------------------------------------------
// Exercise 14.11: RandomAccessHardwareRecord.java
// Subclass of HardwareRecord for random-access file programs.
package org.egan; // package for reuse
import java.io.RandomAccessFile;
import java.io.IOException;
public class RandomAccessHardwareRecord extends HardwareRecord
public static final int SIZE = 46;
// no-argument constructor calls other constructor with default values
public RandomAccessHardwareRecord()
this(0,"",0,0.0);
} // end no-argument RandomAccessHardwareRecord constructor
// initialize a RandomAccessHardwareRecord
public RandomAccessHardwareRecord(int number, String tool, int amount, double price)
super(number,tool,amount,price);
} // end four-argument RandomAccessHardwareRecord constructor
// read a record from a specified RandomAccessFile
public void read(RandomAccessFile file) throws IOException
setRecordNumber(file.readInt());
setToolName(readName(file));
setQuantity(file.readInt());
setCost(file.readDouble());
} // end method read
// ensure that name is proper length
private String readName(RandomAccessFile file) throws IOException
char name[] = new char[15], temp;
for(int count = 0; count < name.length; count++)
temp = file.readChar();
name[count] = temp;
} // end for
return new String(name).replace('\0',' ');
} // end method readName
// write a record to specified RandomAccessFile
public void write(RandomAccessFile file) throws IOException
file.writeInt(getRecordNumber());
writeName(file, getToolName());
file.writeInt(getQuantity());
file.writeDouble(getCost());
} // end method write
// write a name to file; maximum of 15 characters
private void writeName(RandomAccessFile file, String name) throws IOException
StringBuffer buffer = null;
if (name != null)
buffer = new StringBuffer(name);
else
buffer = new StringBuffer(15);
buffer.setLength(15);
file.writeChars(buffer.toString());
} // end method writeName
} // end RandomAccessHardwareRecord-------------------------------------------------------------------------------------------------
// Exercise 14.11: CreateRandomFile.java
// creates random-access file by writing 100 empty records to disk.
import java.io.IOException;
import java.io.RandomAccessFile;
import org.egan.RandomAccessHardwareRecord;
public class CreateRandomFile
private static final int NUMBER_RECORDS = 100;
// enable user to select file to open
public void createFile()
RandomAccessFile file = null;
try // open file for reading and writing
file = new RandomAccessFile("hardware.dat","rw");
RandomAccessHardwareRecord blankRecord = new RandomAccessHardwareRecord();
// write 100 blank records
for (int count = 0; count < NUMBER_RECORDS; count++)
blankRecord.write(file);
// display message that file was created
System.out.println("Created file hardware.dat.");
System.exit(0); // terminate program
} // end try
catch (IOException ioException)
System.err.println("Error processing file.");
System.exit(1);
} // end catch
finally
try
if (file != null)
file.close(); // close file
} // end try
catch (IOException ioException)
System.err.println("Error closing file.");
System.exit(1);
} // end catch
} // end finally
} // end method createFile
} // end class CreateRandomFile-------------------------------------------------------------------------------------------------
// Exercise 14.11: CreateRandomFileTest.java
// Testing class CreateRandomFile
public class CreateRandomFileTest
// main method begins program execution
public static void main( String args[] )
CreateRandomFile application = new CreateRandomFile();
application.createFile();
} // end main
} // end class CreateRandomFileTest-------------------------------------------------------------------------------------------------
// Exercise 14.11: MenuOption.java
// Defines an enum type for the hardware credit inquiry program's options.
public enum MenuOption
// declare contents of enum type
PRINT(1),
UPDATE(2),
NEW(3),
DELETE(4),
END(5);
private final int value; // current menu option
MenuOption(int valueOption)
value = valueOption;
} // end MenuOptions enum constructor
public int getValue()
return value;
} // end method getValue
} // end enum MenuOption-------------------------------------------------------------------------------------------------
// Exercise 14.11: FileEditor.java
// This class declares methods that manipulate hardware account records
// in a random access file.
import java.io.EOFException;
import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.util.Scanner;
import org.egan.RandomAccessHardwareRecord;
public class FileEditor
RandomAccessFile file; // reference to the file
Scanner input = new Scanner(System.in);
// open the file
public FileEditor(String fileName) throws IOException
file = new RandomAccessFile(fileName, "rw");
} // end FileEditor constructor
// close the file
public void closeFile() throws IOException
if (file != null)
file.close();
} // end method closeFile
// get a record from the file
public RandomAccessHardwareRecord getRecord(int recordNumber)
throws IllegalArgumentException, NumberFormatException, IOException
RandomAccessHardwareRecord record = new RandomAccessHardwareRecord();
if (recordNumber < 1 || recordNumber > 100)
throw new IllegalArgumentException("Out of range");
// seek appropriate record in a file
file.seek((recordNumber - 1) * RandomAccessHardwareRecord.SIZE);
record.read(file);
return record;
} // end method getRecord
// update record tool name in file
public void updateRecordToolName(int recordNumber, String newToolName)
throws IllegalArgumentException, IOException
RandomAccessHardwareRecord record = getRecord(recordNumber);
if (record.getRecordNumber() == 0)
throw new IllegalArgumentException("Record does not exist");
// seek appropriate record in file
file.seek((recordNumber - 1) * RandomAccessHardwareRecord.SIZE);
record.setToolName(newToolName);
record = new RandomAccessHardwareRecord(
record.getRecordNumber(), record.getToolName(), record.getQuantity(), record.getCost());
record.write(file); // write updated record to file
} // end method updateRecordToolName
// update record in file
public void updateRecordQuantity(int recordNumber, int newQuantity)
throws IllegalArgumentException, IOException
RandomAccessHardwareRecord record = getRecord(recordNumber);
if (record.getRecordNumber() == 0)
throw new IllegalArgumentException("Record does not exist");
// seek appropriate record in file
file.seek((recordNumber - 1) * RandomAccessHardwareRecord.SIZE);
record.setQuantity(newQuantity);
record = new RandomAccessHardwareRecord(
record.getRecordNumber(), record.getToolName(), record.getQuantity(), record.getCost());
record.write(file); // write updated record to file
} // end method updateRecordQuantity
// update record in file
public void updateRecordCost(int recordNumber, double newCost)
throws IllegalArgumentException, IOException
RandomAccessHardwareRecord record = getRecord(recordNumber);
if (record.getRecordNumber() == 0)
throw new IllegalArgumentException("Record does not exist");
// seek appropriate record in file
file.seek((recordNumber - 1) * RandomAccessHardwareRecord.SIZE);
record.setCost(newCost);
record = new RandomAccessHardwareRecord(
record.getRecordNumber(), record.getToolName(), record.getQuantity(), record.getCost());
record.write(file); // write updated record to file
} // end method updateRecordCost
// add record to file
public void newRecord(int recordNumber, String toolName, int quantity, double cost)
throws IllegalArgumentException, IOException
RandomAccessHardwareRecord record = getRecord(recordNumber);
if (record.getRecordNumber() != 0)
throw new IllegalArgumentException("Record already exists");
// seek appropriate record in file
file.seek((recordNumber - 1) * RandomAccessHardwareRecord.SIZE);
record = new RandomAccessHardwareRecord(recordNumber, toolName, quantity, cost);
record.write(file); // write record to file
} // end method newRecord
// delete record from file
public void deleteRecord(int recordNumber) throws IllegalArgumentException, IOException
RandomAccessHardwareRecord record = getRecord(recordNumber);
if (record.getRecordNumber() == 0)
throw new IllegalArgumentException("Account does not exist");
// seek appropriate record in file
file.seek((recordNumber - 1) * RandomAccessHardwareRecord.SIZE);
// create a blank record to write to the file
record = new RandomAccessHardwareRecord();
record.write(file);
} // end method deleteRecord
// read and display records
public void readRecords()
RandomAccessHardwareRecord record = new RandomAccessHardwareRecord();
System.out.printf("%-10s%-15s%-15s%10s\n","Record","Tool Name","Quantity","Cost");
try // read a record and display
file.seek(0);
while (true)
do
record.read(file);
while (record.getRecordNumber() == 0);
// display record contents
System.out.printf("%-10d%-15s%-15d%10.2f\n",record.getRecordNumber(),
record.getToolName(), record.getQuantity(), record.getCost());
} // end while
} // end try
catch (EOFException eofException) // close file
return; // end of file was reached
} // end catch
catch (IOException ioException)
System.err.println("Error reading file.");
System.exit(1);
} // end catch
} // end method readRecords
} // end class FileEditor-------------------------------------------------------------------------------------------------
// Exercise 14.11: TransactionProcessor.java
// A transaction processing program using random-access files.
import java.io.IOException;
import java.util.NoSuchElementException;
import java.util.Scanner;
import org.egan.RandomAccessHardwareRecord;
public class TransactionProcessor
private FileEditor dataFile;
private RandomAccessHardwareRecord record;
private MenuOption choices[] = {MenuOption.PRINT, MenuOption.UPDATE, MenuOption.NEW,
MenuOption.DELETE, MenuOption.END};
private Scanner input = new Scanner(System.in);
// get the file name and open the file
private boolean openFile()
try // attempt to open file
// call the helper method to open the file
dataFile = new FileEditor("hardware.dat");
} // end try
catch (IOException ioException)
System.err.println("Error opening file.");
return false;
} // end catch
return true;
} // end method openFile
// close file and terminate application
private void closeFile()
try // close file
dataFile.closeFile();
} // end try
catch (IOException ioException)
System.err.println("Error closing file.");
System.exit(1);
} // end catch
} // end method closeFile
// create, update or delete the record
private void performAction(MenuOption action)
int recordNumber = 0; // record number of record
String toolName; // tool name of the hardware instrument
int quantity; // total amount of items
double cost; // hareware tool price
int choice; // choose an update option
int newRecordNumber; // the updated record number
String newToolName; // the updated tool name
int newQuantity; // the updated quantity
double newCost; // the updated cost
try // attempt to manipulate files based on option selected
switch(action) // switch based on option selected
case PRINT:
System.out.println();
dataFile.readRecords();
break;
case NEW:
System.out.printf("\n%s%s\n%s\n%s","Enter record number,",
"tool name, quantity, and cost.","(Record number must be 1 - 100)","? ");
recordNumber = input.nextInt(); // read record number
toolName = input.next(); // read tool name
quantity = input.nextInt(); // read quantity
cost = input.nextDouble(); // read cost
dataFile.newRecord(recordNumber, toolName, quantity, cost); // create new record
break;
case UPDATE:
System.out.print("\nEnter record number to update (1 - 100): ");
recordNumber = input.nextInt();
record = dataFile.getRecord(recordNumber);
if (record.getRecordNumber() == 0)
System.out.println("Record does not exist.");
else
// display record contents
System.out.printf("%-10d%-12s%-12d%10.2f\n\n", record.getRecordNumber(),
record.getToolName(), record.getQuantity(), record.getCost());
System.out.printf("%s%s","\nEnter 1 to update tool name, ",
"2 to update quantity, or 3 to update cost : ");
choice = input.nextInt();
if (choice == 1)
System.out.print("Enter new record tool name : ");
newToolName = input.next();
dataFile.updateRecordToolName(recordNumber,newToolName); // update record
// tool name
// retrieve updated record
record = dataFile.getRecord(recordNumber);
// display updated record
System.out.printf("%-10d%-12s%-12d%10.2f\n", record.getRecordNumber(),
record.getToolName(), record.getQuantity(), record.getCost());
else if (choice == 2)
System.out.print("Enter new record quantity : ");
newQuantity = input.nextInt();
dataFile.updateRecordQuantity(recordNumber,newQuantity); // update record
// quantity
// retrieve updated record
record = dataFile.getRecord(recordNumber);
// display updated record
System.out.printf("%-10d%-12s%-12d%10.2f\n", record.getRecordNumber(),
record.getToolName(), record.getQuantity(), record.getCost());
else if (choice == 3)
System.out.print("Enter new record cost : ");
newCost = input.nextDouble();
dataFile.updateRecordCost(recordNumber,newCost); // update record cost
// retrieve updated record
record = dataFile.getRecord(recordNumber);
// display updated record
System.out.printf("%-10d%-12s%-12d%10.2f\n", record.getRecordNumber(),
record.getToolName(), record.getQuantity(), record.getCost());
} // end else
break;
case DELETE:
System.out.print("\nEnter an account to delete ( 1 - 100): ");
recordNumber = input.nextInt();
dataFile.deleteRecord(recordNumber); // delete record
break;
default:
System.out.println("Invalid action.");
break;
} // end switch
} // end try
catch (NumberFormatException format)
System.err.println("Bad input.");
} // end catch
catch (IllegalArgumentException badRecord)
System.err.println(badRecord.getMessage());
} // end catch
catch (IOException ioException)
System.err.println("Error writing to the file.");
} // end catch
catch (NoSuchElementException elementException)
System.err.println("Invalid input. Please try again.");
input.nextLine();
} // end catch
} // end method performAction
// enable user to input menu choice
private MenuOption enterChoice()
int menuChoice = 1;
// display available options
System.out.printf("\n%s\n%s\n%s\n%s\n%s\n%s","Enter your choice",
"1 - List hardware records", "2 - Update a hardware record",
"3 - Add a new hardware record", "4 - Delete a hardware record", "5 - End program\n?");
try
menuChoice = input.nextInt();
catch (NoSuchElementException elementException)
System.err.println("Invalid input.");
System.exit(1);
} // end catch
return choices[menuChoice - 1]; // return choice from user
} // end enterChoice
public void processRequests()
openFile();
// get user's request
MenuOption choice = enterChoice();
while (choice != MenuOption.END)
performAction(choice);
choice = enterChoice();
} // end while
closeFile();
} // end method processRequests
} // end class TransactionProcessor-------------------------------------------------------------------------------------------------
// Exercise 14.11: TransactionProcessorTest.java
// Testing the transaction processor.
public class TransactionProcessorTest
public static void main(String args[])
TransactionProcessor application = new TransactionProcessor();
application.processRequests();
} // end main
} // end class TransactionProcessorTest-------------------------------------------------------------------------------------------------
Below is the sample data to be entered into the random input file hardware.dat :
Record Tool Quantity Cost
Number Name
3 Sander 18 35.99
19 Hammer 128 10.00
26 Jigsaw 16 14.25
39 Mower 10 79.50
56 Saw 8 89.99
76 Screwdriver 236 4.99
81 Sledgehammer 32 19.75
88 Wrench 65 6.48Message was edited by:
egan128
Message was edited by:
egan128
Message was edited by:
egan128Hi Does anyone know if I can modify the record number
in the random access file hardware.dat for each
hardware record each time and update it in
hardware.dat to display it?If the "record number" is data that is stored in the file, then you can modify it. More precisely: it is possible to modify it.
The rest of the question had too many incompatible verbs for me to understand it.
Also why does it say
"Record does not exist" if I modify the record number
for a hardware and try to update it but could not
find that record?"Record does not exist" is a fairly reasonable error message for the situation where a program looks for a record but cannot find it. Are you asking why that particular lump of code actually does that?
(One thousand lines of code removed) -
Xml elements random access table
hi all,
i'm having a random access table holdin the index for each xml node in a xml file, any idea how can u access the xml node directly without going through the whole xml file. i want to do this by either sax or stax, dom is not valid with my case. thanxeng_cs wrote:
hi all,
i'm having a random access table holdin the index for each xml node in a xml file, any idea how can u access the xml node directly without going through the whole xml file. i want to do this by either sax or stax, dom is not valid with my case. thanxI far as I know you could only accomplish such a thing using DOM parser alone, as DOM supports XPATH. SAX or StAX do not support XPATH, so directly going to the node in a xml is not possible using SAX or StAX. -
How to use random access file to access file in disk?
I have tried to use random access file stream to access the some files saved in disk, but not very successful. I want to know how I can find a particular file in the disk with file locator or sth else.
Suggestion is highly welcomed, if you have codes to put, I will test it.The scenerao is:
create a randomAccessfile
write 100 blank records( for future use)
open this file
write data to the records inside file
close the file.
I will try to put a testing code for you later on. -
Randomly accessing serialized objects
Is there any way to access objects written to a file randomly. Serialization basically needs accessing objects in the same order as they are writeen. but i need to access object(s) in any order.
Any suggestions on how to do so?I got this reply when i questioned the person
incharge...may be theres much more to it than i
could specify..........It could also be the case that the person in charge doesn't know that there are databases with small footprints implemented in java.
so i would be glad if soemone
could tell me what ever i plan to do with respect to
random accessing is possible or not.....I think that you should be able to write all objects to one stream, and do a reset (on the object output stream) between each write, and write the start position of each object into an index file.
I'm not sure that it will work, and having a data file + an index file is like having a small database (so why not download a database in that case)
/Kaj -
Please Come IN! IanSchneider. About random access serialized objects.
Hi,I'm a freshman.
I have a question about serialized objects.
If I useing writeObject() serialize objects into a file in order,I can gain them with readObject() in the same order. But if I want to random access these serialized objects rather than one by one,how to do?
Mr IanSchneider said "write all your objects into the same file using normal io techniques and you can still generate an index and acheive random access". It seems easy,but how to generate index and use it to acheive random access? Please write something in detail,Thank you in advance!
EXPECTING��Have a look at this class: [ [u]WARNING: I just wrote this code, it hasn't been tested ]
import java.io.BufferedInputStream;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.RandomAccessFile;
import java.io.Serializable;
import java.util.ArrayList;
public class SerializedObjectWriter {
private RandomAccessFile raf;
private String filepath;
private String mode;
public SerializedObjectWriter(String filePath, String mode) throws FileNotFoundException {
this.filepath = filePath;
this.mode = mode;
this.raf = new RandomAccessFile(filePath, mode);
public void writeObject(Object o, long pos) throws IOException {
raf.seek(pos);
final byte[] bytes = serialize((Serializable)o);
raf.writeInt(bytes.length);
raf.write(bytes);
public void append(Object o) throws IOException {
writeObject(o, raf.length());
public Object readObject(long pos) throws IOException, ClassNotFoundException {
raf.seek(pos);
int len = raf.readInt();
final byte[] data = new byte[len];
raf.readFully(data);
return deSerialize(data);
public Object[] readAllObjects() throws IOException, ClassNotFoundException {
int pos = 0;
final ArrayList al = new ArrayList();
while (true) {
raf.seek(pos);
final int len = raf.readInt();
final byte[] data = new byte[len];
raf.readFully(data);
al.add(deSerialize(data));
pos = (pos + len + 4);
if (pos >= raf.length()) break;
return al.toArray();
public long length() throws IOException {
return raf.length();
public void reset() throws IOException {
raf.close();
final boolean success = new File(filepath).delete();
if (!success) throw new IOException("Failed to delete file");
raf = new RandomAccessFile(filepath, mode);
public void close() throws IOException {
raf.close();
private byte[] serialize(Serializable obj) throws IOException {
final ByteArrayOutputStream baos = new ByteArrayOutputStream();
final ObjectOutputStream oos = new ObjectOutputStream(baos);
try {
oos.writeObject(obj);
} finally {
oos.close();
return baos.toByteArray();
private Object deSerialize(byte[] data) throws IOException, ClassNotFoundException {
final ByteArrayInputStream bais = new ByteArrayInputStream(data);
final BufferedInputStream bis = new BufferedInputStream(bais);
final ObjectInputStream ois = new ObjectInputStream(bis);
try {
return (Serializable) ois.readObject();
} finally {
ois.close();
public static void main(String[] args) throws Exception {
SerializedObjectWriter sor = new SerializedObjectWriter("C:\\test.ser", "rw");
sor.reset();
sor.writeObject("Test 1", 0);
sor.append("Test 2");
sor.append("Test 3");
Object[] objects = sor.readAllObjects();
for (int i = 0; i < objects.length; i++) {
System.out.println(objects);
sor.close();
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Hello, When I connect my iPad 1 with a wide screen TV using the apple VGA connector, there's no display on the TV. But when I do the same thing from iPad 2, the iPad screen is projected on TV. Please help
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Someone has just hacked into my itunes account.
They bought 'Kingdom Conquest'. which all together was worth $58.00. How can i get my money back?
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Selling my macbook, buying a new one. What do I do with my iPhone?
I'm selling my macbook. I already bought a new MacBook Pro. The problem is that I don't know what to do with my iPhone account. How can I move my music, photos, apps, and contacts to my MBP? Is there any possible way to do all this?
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Query Generator Variable Alias
Hi, How can I create an alias for variables in scripts made with query generator? For example, if i include where clauses such as begin date and end date using greater/less than, they will be both shown in the criteria selection box as "Posting Date.
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I can't see photos on Facebook.What should i do?
When i open facebook i can't pictures except the profile pictures.