Difference between IS NULL and = NULL

Hello Guys,
In 10gR2 what is the difference between IS NULL and = NULL
Thanks,
Imran

Just don't use the second, because the comparison operator = cannot deal with NULLs as you (probably) hope it can:
SQL> create table t1 as select rownum as id, 'test' as word from dual connect by level<=2;
Table created.
SQL> update t1 set word=null where id=1;
1 row updated.
SQL> commit;
Commit complete.
SQL> select * from t1;
        ID WORD
         1
         2 test
SQL> select * from t1 where word is null;
        ID WORD
         1
SQL> select * from t1 where word = null;
no rows selectedKind regards
Uwe Hesse
http://uhesse.wordpress.com

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UIX 2.2.8: Difference between bc4j:_null and null/

Anyone here who can explain me the difference between <boundAttribute name="attrName">
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</boundAttribute> and <boundAttribute name="attrName">
<null/>
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Thanks, Markus

ping

Difference between Null and null?

What is the difference between null and NULL?
When is each used?
Thanks,

veryConfused wrote:
There is a null in java, but no NULL. null means no value. However, when assigning value, the following is different:Although the empty String has no special role. Null means, the referential type is not assigned (doesn't refer) to a specific object. The empty String is just another object though, so seeing it or pointing it out as something special when it actually isn't at all (no more special than new Integer(0) or new Object[0]) just adds to the confusion.

What's difference between JPanel.remove(); and JPanel = null

nice day,
how can remove JPanel (including its JComponents), safe way, can you explain the difference between JPanel.remove () and JPanel = null,
1/ because if JPanel does not contain any static JComponents
2/ or any reference to static objects,
then works as well as JPanel.remove or JPanel = null,
or what and why preferred to avoid some action (to avoid to remove or to avoid to null)

mKorbel wrote:
nice day,
how can remove JPanel (including its JComponents), safe way, can you explain the difference between JPanel.remove () and JPanel = null, Remove the JPanel from the container it was part of and make sure you do not keep any references to it from your own classes. Don't make it any more difficult than it has to be.

What is the difference between string != null and null !=string ?

Hi,
what is the difference between string != null and null != string ?
which is the best option ?
Thanks
user8729783

Like you've presented it, nothing. There is no difference and neither is the "better option".

Difference between PRIMARY KEY and UNIQUE KEY with NOT NULL

What is the difference between PRIMARY KEY and UNIQUE KEY with NOT NULL constraint?
Message was edited by:
Nilesh Hole

Answer for the master!!!
http://asktom.oracle.com/pls/asktom/f?p=100:11:0::::P11_QUESTION_ID:8743855576462
Thanks,
Karthick

Difference between conn.close() and conn=null;

Hi All,
Can anybody please let me know the difference between conn.close()
and conn=null;
where conn is reference to Connection.
Thanks and Regards
-sunjavadeveloper

Thanks for your response.
Is there any other good approach to close() & then
null the Obj. can u give us your opinion.
          finally
            try{
                     if(dbconn != null)     dbconn.close();
                     if(stmt != null) stmt.close();
                     if(rs != null) rs.close();
                     if(con != null) con.close();
            catch (Exception e)
                   logger.fatal(e.getMessage(),e);
throw new Exception ("Exception -- Vendor.java --
a -- authenticate -- " + e.getMessage() );
               dbconn = null;
               rs = null;
               stmt=null;
               con = null;
Putting the close() calls in finally block is good, but having them in individual try/catch blocks is better. That way you can still try to close the connection if closing the statement throws an exception.
I don't bother setting them to null. GC is smart enough to know that they've gone out of scope. I don't think it helps.
%

Difference between Unique key and Primary key(other than normal difference)

Hello,
1).Can any one tell me any other difference between Unique key and Primary key other than it having NULLs.
2). What is the difference the words 'DISTINCT' and 'UNIQUE' in a sql query.
Thanks in advance.

Hi
If you don't believe me than see the documentation in
OTN.
Ott Karesz
http://www.trendo-kft.hu
SQL> create table scott.tbl_clob
2 (sss CLOB)
3 /
Tabelle wurde angelegt.
SQL> insert into scott.tbl_clob values('wrwrwrw')
2 /
1 Zeile wurde erstellt.
SQL> insert into scott.tbl_clob values('wrwrwrw')
2 /
1 Zeile wurde erstellt.
SQL> select distinct sss from scott.tbl_clob
2 /
select distinct sss from scott.tbl_clob
FEHLER in Zeile 1:
ORA-00932: nicht übereinstimmende Datentypen
SQL> select unique sss from scott.tbl_clob
2 /
select unique sss from scott.tbl_clob
FEHLER in Zeile 1:
ORA-00932: nicht übereinstimmende Datentypen
SQL> select distinct to_char(sss) from scott.tbl_clob
2 /
TO_CHAR(SSS)
wrwrwrw
SQL> select unique to_char(sss) from scott.tbl_clob
2 /
TO_CHAR(SSS)
wrwrwrw
SQL>

Question about main difference between Java bean and Java class in JSP

Hi All,
I am new to Java Bean and wonder what is the main difference to use a Bean or an Object in the jsp. I have search on the forum and find some post also asking the question but still answer my doubt. Indeed, what is the real advantage of using bean in jsp.
Let me give an example to illustrate my question:
<code>
<%@ page errorPage="errorpage.jsp" %>
<%@ page import="ShoppingCart" %>

<jsp:useBean id="cart" scope="session" class="ShoppingCart" />
<html>
<head><title>Shopping Cart</title></head>
<body bgcolor="#FFFFFF">
Your cart's ID is: <%=cart.getId()%>.
</body>
<html>
</code>
In the above code, I can also create a object of ShoppingCart by new operator then get the id at the following way.
<code>
<%
ShoppingCart cart = new ShoppingCart();
out.println(cart.getId());
%>
</code>
Now my question is what is the difference between the two method? As in my mind, a normal class can also have it setter and getter methods for its properties. But someone may say that, there is a scope="session", which can be declared in an normal object. It may be a point but it can be easily solved but putting the object in session by "session.setAttribute("cart", cart)".
I have been searching on this issue on the internet for a long time and most of them just say someting like "persistance of state", "bean follow some conventions of naming", "bean must implement ser" and so on. All of above can be solved by other means, for example, a normal class can also follow the convention. I am really get confused with it, and really want to know what is the main point(s) of using the java bean.
Any help will be highly apprecaited. Thanks!!!
Best Regards,
Alex

Hi All,
I am new to Java Bean and wonder what is the main
difference to use a Bean or an Object in the jsp. The first thing to realize is that JavaBeans are just Plain Old Java Objects (POJOs) that follow a specific set of semantics (get/set methods, etc...). So what is the difference between a Bean and an Object? Nothing.
<jsp:useBean id="cart" scope="session" class="ShoppingCart" />
In the above code, I can also create a object of
ShoppingCart by new operator then get the id at the
following way.
ShoppingCart cart = new ShoppingCart();
out.println(cart.getId());
...Sure you could. And if the Cart was in a package (it has to be) you also need to put an import statement in. Oh, and to make sure the object is accessable in the same scope, you have to put it into the PageContext scope. And to totally equal, you first check to see if that object already exists in scope. So to get the equivalant of this:
<jsp:useBean id="cart" class="my.pack.ShoppingCart"/>Then your scriptlet looks like this:
<%@ page import="my.pack.ShoppingCart %>
<%
ShoppingCart cart = pageContext.getAttribute("cart");
if (cart == null) {
    cart = new ShoppingCart();
    pageContext.setAttribute("cart", cart);
%>So it is a lot more work.
As in my mind, a normal class can also
have it setter and getter methods for its properties.True ... See below.
But someone may say that, there is a scope="session",
which can be declared in an normal object.As long as the object is serializeable, yes.
It may be
a point but it can be easily solved but putting the
object in session by "session.setAttribute("cart",
cart)".Possible, but if the object isn't serializable it can be unsafe. As the point I mentioned above, the useBean tag allows you to check if the bean exists already, and use that, or make a new one if it does not yet exist in one line. A lot easier than the code you need to use otherwise.
I have been searching on this issue on the internet
for a long time and most of them just say someting
like "persistance of state", "bean follow some
conventions of naming", "bean must implement ser" and
so on. Right, that would go along the lines of the definition of what a JavaBean is.
All of above can be solved by other means, for
example, a normal class can also follow the
convention. And if it does - then it is a JavaBean! A JavaBean is any Object whose class definition would include all of the following:
1) A public, no-argument constructor
2) Implements Serializeable
3) Properties are revealed through public mutator methods (void return type, start with 'set' have a single Object parameter list) and public accessor methods (Object return type, void parameter list, begin with 'get').
4) Contain any necessary event handling methods. Depending on the purpose of the bean, you may include event handlers for when the properties change.
I am really get confused with it, and
really want to know what is the main point(s) of
using the java bean.JavaBeans are normal objects that follow these conventions. Because they do, then you can access them through simplified means. For example, One way of having an object in session that contains data I want to print our might be:
<%@ page import="my.pack.ShoppingCart %>
<%
ShoppingCart cart = session.getAttribute("cart");
if (cart == null) {
    cart = new ShoppingCart();
    session.setAttribute("cart", cart);
%>Then later where I want to print a total:
<% out.print(cart.getTotal() %>Or, if the cart is a JavaBean I could do this:
<jsp:useBean id="cart" class="my.pack.ShoppingCart" scope="session"/>
Then later on:
<jsp:getProperty name="cart" property="total"/>
Or perhaps I want to set some properties on the object that I get off of the URL's parameter group. I could do this:
<%
ShoppingCart cart = session.getAttribute("cart");
if (cart == null) {
    cart = new ShoppingCart();
    cart.setCreditCard(request.getParameter("creditCard"));
    cart.setFirstName(request.getParameter("firstName"));
    cart.setLastName(request.getParameter("lastName"));
    cart.setBillingAddress1(request.getParameter("billingAddress1"));
    cart.setBillingAddress2(request.getParameter("billingAddress2"));
    cart.setZipCode(request.getParameter("zipCode"));
    cart.setRegion(request.getParameter("region"));
    cart.setCountry(request.getParameter("country"));
    pageContext.setAttribute("cart", cart);
    session.setAttribute("cart", cart);
}Or you could use:
<jsp:useBean id="cart" class="my.pack.ShoppingCart" scope="session">
<jsp:setProperty name="cart" property="*"/>
</jsp:useBean>The second seems easier to me.
It also allows you to use your objects in more varied cases - for example, JSTL (the standard tag libraries) and EL (expression language) only work with JavaBeans (objects that follow the JavaBeans conventions) because they expect objects to have the no-arg constuctor, and properties accessed/changed via getXXX and setXXX methods.
>
Any help will be highly apprecaited. Thanks!!!
Best Regards,
Alex

Difference between Data staging and Dimension Table ?

Difference between Data staging and Dimension Table ?

Data Staging:
Data extraction and transformation is done here.
Meaning that, if we have source data in flat file, we extract it and load into staging tables, we take care of nulls, we change datetime format etc.. and after such cleansing/transformation at then end, load it to Dim/Fact tables
Pros: Makes process simpler and easy and also we can keep track of data as we have data in staging
Cons: Staging tables need space hence need memory space
Dimension Table:
tables which describes/stores the attribute about specific objects
Below is star schema which has dimension storing information related to Product, Customer etc..
-Vaibhav Chaudhari

I want to know the difference between Days column and Day1 Column

Hi All,
I used this query:
SELECT to_char(return_date_time,'dd/mon/yyyy hh24:mi:ss') Test,
DECODE ('I', 'I', DECODE (1, NULL, NULL, 0, NULL, SYSDATE + 1)) Days,
DECODE ('I', 'I', SYSDATE + 1) Day1
FROM fm_curr_locn
WHERE patient_id = 'DU00002765'
output:
Test
Days
Day1
26/oct/2013 00:00:00
26-OCT-13
10/26/2013 3:06:59 PM
I want to know the difference between Days column and Day1 column and why the days column didnt show the time
Please anyone help.....
Regards
Shagar M

Pleiadian wrote:
It is the decode statement that is doing this.
The format of decode is:
decode(expression, search1, result1, search2, result2, searchn, resultn, default)
All result fields must be of the same datatype and will be of the datatype of the first result (result1 in this example)
In your example (the decode for the field Days) the first result is a NULL. I suspect (gurus? anyone?) that Oracle will use the varchar2 overload of the decode statement, and the date field will be converted to varchar2 using your NLS_DATE_FORMAT settings.
In the second decode statment (Day1) the first result is of datatype date, so the result of the decode statement will be a date field (and will be parsed as such by your sql development tool)
I agree, as NULL is the first result returned the datatype is undetermined, so Oracle is picking VARCHAR2 over others, and causing an implicit datatype conversion on the resultant date value, whereas the other which is returned as a date will use the local settings of the client tool being used.
I can replicate the 'issue' in Toad, and it's rectified if we cast the first returned value of the decode statement...
SELECT DECODE ('I', 'I', DECODE (1, NULL, CAST(NULL AS DATE), 0, NULL, SYSDATE + 1)) Days,
DECODE ('I', 'I', SYSDATE + 1) Day1
FROM dual

Difference between wait event and timed event

Hi,
Anyone has idea that what is the difference between wait events and timed events in Statspack report. I couldn't find it over google.
Thanks.

It's 10.2.0.1 on Linux
(Couldn't do a query, because Linux is inside VM Ware. And it is not being accessed from Base windows machine.)
Top 5 Timed Events Avg %Total
~~~~~~~~~~~~~~~~~~ wait Call
Event Waits Time (s) (ms) Time
db file scattered read 9,750,617 34,611 4 44.7
CPU time 14,248 18.4
read by other session 1,532,282 8,984 6 11.6
db file sequential read 4,514,494 5,588 1 7.2
latch: cache buffers lru chain 277,245 4,823 17 6.2
Wait Events DB/Inst: ABCD/ABCD Snaps: 1-2
-> s - second, cs - centisecond, ms - millisecond, us - microsecond
-> %Timeouts: value of 0 indicates value was < .5%. Value of null is truly 0
-> Only events with Total Wait Time (s) >= .001 are shown
-> ordered by Total Wait Time desc, Waits desc (idle events last)
Avg
%Time Total Wait wait Waits
Event Waits -outs Time (s) (ms) /txn
db file scattered read 9,750,617 0 34,611 4 24.2
read by other session 1,532,282 0 8,984 6 3.8
db file sequential read 4,514,494 0 5,588 1 11.2
latch: cache buffers lru chain 277,245 0 4,823 17 0.7
latch free 121,466 0 3,291 27 0.3
----------------------------------------------------------------------------------------------------

Difference between inner join and outer join

1.Difference between inner join and outer join
2.wht is the difference in using hide and get crusor value in interactive.
3. Using join is better or views in writting program . Which is better.

Table 1                      Table 2
A
B
C
D
D
E
F
G
H
a1
b1
c1
1
1
e1
f1
g1
h1
a2
b2
c2
1
3
e2
f2
g2
h2
a3
b3
c3
2
4
e3
f3
g3
h3
a4
b4
c4
3
|--|||--|
    Inner Join
    |--||||||||--|
    | A | B | C | D | D | E | F | G | H |
    |--||||||||--|
    | a1 | b1 | c1 | 1 | 1 | e1 | f1 | g1 | h1 |
    | a2 | b2 | c2 | 1 | 1 | e1 | f1 | g1 | h1 |
    | a4 | b4 | c4 | 3 | 3 | e2 | f2 | g2 | h2 |
    |--||||||||--|
Example
Output a list of all flights from Frankfurt to New York between September 10th and 20th, 2001 that are not sold out:
DATA: DATE   LIKE SFLIGHT-FLDATE,
      CARRID LIKE SFLIGHT-CARRID,
      CONNID LIKE SFLIGHT-CONNID.
SELECT FCARRID FCONNID F~FLDATE
    INTO (CARRID, CONNID, DATE)
    FROM SFLIGHT AS F INNER JOIN SPFLI AS P
           ON FCARRID = PCARRID AND
              FCONNID = PCONNID
    WHERE P~CITYFROM = 'FRANKFURT'
      AND P~CITYTO   = 'NEW YORK'
      AND F~FLDATE BETWEEN '20010910' AND '20010920'
      AND FSEATSOCC < FSEATSMAX.
WRITE: / DATE, CARRID, CONNID.
ENDSELECT.
If there are columns with the same name in both tables, you must distinguish between them by prefixing the field descriptor with the table name or a table alias.
Note
In order to determine the result of a SELECT command where the FROM clause contains a join, the database system first creates a temporary table containing the lines that meet the ON condition. The WHERE condition is then applied to the temporary table. It does not matter in an inner join whether the condition is in the ON or WHEREclause. The following example returns the same solution as the previous one.
Example
Output of a list of all flights from Frankfurt to New York between September 10th and 20th, 2001 that are not sold out:
DATA: DATE   LIKE SFLIGHT-FLDATE,
      CARRID LIKE SFLIGHT-CARRID,
      CONNID LIKE SFLIGHT-CONNID.
SELECT FCARRID FCONNID F~FLDATE
    INTO (CARRID, CONNID, DATE)
    FROM SFLIGHT AS F INNER JOIN SPFLI AS P
           ON FCARRID = PCARRID
    WHERE FCONNID = PCONNID
      AND P~CITYFROM = 'FRANKFURT'
      AND P~CITYTO   = 'NEW YORK'
      AND F~FLDATE BETWEEN '20010910' AND '20010920'
      AND FSEATSOCC < FSEATSMAX.
WRITE: / DATE, CARRID, CONNID.
ENDSELECT.
Note
Since not all of the database systems supported by SAP use the standard syntax for ON conditions, the syntax has been restricted. It only allows those joins that produce the same results on all of the supported database systems:
Only a table or view may appear to the right of the JOIN operator, not another join expression.
Only AND is possible in the ON condition as a logical operator.
Each comparison in the ON condition must contain a field from the right-hand table.
If an outer join occurs in the FROM clause, all the ON conditions must contain at least one "real" JOIN condition (a condition that contains a field from tabref1 amd a field from tabref2.
Note
In some cases, '*' may be specified in the SELECT clause, and an internal table or work area is entered into the INTO clause (instead of a list of fields). If so, the fields are written to the target area from left to right in the order in which the tables appear in the FROM clause, according to the structure of each table work area. There can then be gaps between table work areas if you use an Alignment Request. For this reason, you should define the target work area with reference to the types of the database tables, not simply by counting the total number of fields. For an example, see below:
Variant 3
... FROM tabref1 LEFT [OUTER] JOIN tabref2 ON cond
Effect
Selects the data from the transparent database tables and/or views specified in tabref1 and tabref2. tabref1 und tabref2 both have either the same form as in variant 1 or are themselves join expressions. The keyword OUTER can be omitted. The database tables or views specified in tabref1 and tabref2 must be recognized by the ABAP-Dictionary.
In order to determine the result of a SELECT command where the FROM clause contains a left outer join, the database system creates a temporary table containing the lines that meet the ON condition. The remaining fields from the left-hand table (tabref1) are then added to this table, and their corresponding fields from the right-hand table are filled with ZERO values. The system then applies the WHERE condition to the table.
Left outer join between table 1 and table 2 where column D in both tables set the join condition:
Table 1                      Table 2
A
B
C
D
D
E
F
G
H
a1
b1
c1
1
1
e1
f1
g1
h1
a2
b2
c2
1
3
e2
f2
g2
h2
a3
b3
c3
2
4
e3
f3
g3
h3
a4
b4
c4
3
|--|||--|
    Left Outer Join
    |--||||||||--|
    | A | B | C | D | D | E | F | G | H |
    |--||||||||--|
    | a1 | b1 | c1 | 1 | 1 | e1 | f1 | g1 | h1 |
    | a2 | b2 | c2 | 1 | 1 | e1 | f1 | g1 | h1 |
    | a3 | b3 | c3 | 2 |NULL|NULL|NULL|NULL|NULL|
    | a4 | b4 | c4 | 3 | 3 | e2 | f2 | g2 | h2 |
    |--||||||||--|
Regards
Prabhu

Difference between relational integrity and data intigrity

hi
could anybody tell me
what is the difference between
relational integrity and data intigrity
tahnx
kals.

hi,
Data Integrity
Data integrity means, in part, that you can correctly and consistently navigate and manipulate the tables in the database. There are two basic rules to ensure data integrity; entity integrity and referential integrity.
The entity integrity rule states that the value of the primary key can never be a null value (a null value is one that has no value and is not the same as a blank). Because a primary key is used to identify a unique row in a relational table, its value must always be specified and should never be unknown. The integrity rule requires that insert, update, and delete operations maintain the uniqueness and existence of all primary keys.
The referential integrity rule states that if a relational table has a foreign key, then every value of the foreign key must either be null or match the values in the relational table in which that foreign key is a primary key.
What is a Relational Integrity?
A relational database contains tables of data which are related to each other. For example, articles are related to the author who wrote them, and conversely, authors are related to the articles they wrote. (Sounds obvious, and it is.) That's the relational part.
When we work with a relational database, we naturally expect that data in related tables stay related. For example, articles written by MartinB should always be related to MartinB and never be confused with articles written by any other author. That's the integrity part.
Relational Integrity is also called Referential Integrity, perhaps because the mechanism for ensuring integrity is implemented by the way the tables reference each other. Both terms are okay with me. I usually just say RI anyway.
Regards,
Sourabh

Difference between the user_bytes and the bytes of dba_data_files

What's the difference between the user_bytes and the bytes column of the dba_data_file view?

Hi,
>>Bytes : Size Occupied
No. The size of the datafile. Doesn't matter free or used space.
>>User Bytes: Size available for Occupying.
No and Yes. Keep in mind that it shows the total size of the file available for user data since it was creation minus the related metadata information.
In resume, take a look at below:
You can see below, that datafile has 1,500 MB of size but it has 1,499.9375 MB available for user data.
LEGATTI@ORACLE10> select file_id,file_name,bytes,user_bytes from dba_data_files where tablespace_name='USERS2';
   FILE_ID FILE_NAME                                         BYTES USER_BYTES
         7 /u02/oradata/DB01/user02.dbf                 1572864000 1572798464
LEGATTI@ORACLE10> SELECT Substr(df.tablespace_name,1,20) "Tablespace Name",
2         Substr(df.file_name,1,40) "File Name",
3         Round(df.bytes/1024/1024,2) "Size (M)",
4         df.increment_by "Increment By",
5         Round(e.used_bytes/1024/1024,2) "Used (M)",
6         Round(f.free_bytes/1024/1024,2) "Free (M)"
7 FROM   DBA_DATA_FILES DF,
8         (SELECT file_id,
9                 Sum(Decode(bytes,NULL,0,bytes)) used_bytes
10          FROM dba_extents
11          GROUP by file_id) E,
12         (SELECT Max(bytes) free_bytes,
13                 file_id
14          FROM dba_free_space
15          GROUP BY file_id) f
16 WHERE e.file_id (+) = df.file_id
17 AND    df.file_id = f.file_id (+)
18 AND    df.file_id = 7
19 ORDER BY df.tablespace_name,
20           df.file_name;
Now, you can see that just 874 MB has been used from 1,499.9375 MB real space available.
Tablespace Name      File Name                                  Size (M) Increment By   Used (M)   Free (M)
USERS2               /u02/oradata/DB01/user02.dbf                  1,500            0     874.88     625,05Now, is that clear?
Cheers
Legatti

Difference between IS NULL and = NULL

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