Comparing two ResultSets for equality
Hello,
I wish to test if two separate ResultSet objects are identical.
By identical I mean that two different ResultSet objects are identical if
they contain the same rows in the same order, and each row contains identical values in the two ResultSets.
Two possibilities could be that the equals() method returns true or that the hashcode() method also produces the same hash value if the objects are identical as described.
I haven't been able to find any documentation on this issue.
Does anyone know if either (or both) of these methods have the contract as described above? If so are they guaranteed?
I can see several potential problems here. Performance with a large ResultSet, duplicate rows, and the ordering of rows not being guaranteed?
Thanks in advance.
Tim
Two possibilities could be that the equals() method
returns true or that the hashcode() method also
produces the same hash value if the objects are
identical as described.I can tell you without looking anything up that these methods do not do that, as doing that would require them to scan the entire result-set, and JDBC tries to avoid doing useless processing. You are going to have to write this code yourself.
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??how to compare two resultsets??
hi all!
i need to find out whether two resultsets contain the same data.
the only way i know how to do it in java is to put them into a while loop and fetch the contents first and then compare the contents.
but is there an easier way to compare resultsets?
does anyone know how to compare two resultsets without extracting the data?
the code example here executes two identical queries on an oracle database, compare and print the resultsets.
public ResultSet getResultset(String query)
ResultSet rs=null;
try { rs=Stmt.executeQuery(query); }
catch(Exception e) { e.printStackTrace(); }
return rs;
public static void main(String[] args) {
ResultSet r1=null;
ResultSet r2=null;
try {
database db = new ddatabase();
r1=db.getResultset("Select 'name' from person");
r2=db.getResultset("Select 'name' from person");
if (r1 == r2) {
System.out.println("ok");
System.out.print(r1);
System.out.println();
System.out.print(r2);
else {
System.out.println("not ok");
System.out.print(r1);
System.out.println();
System.out.print(r2);
jdbc.cleanup();
catch(Exception e) {e.printStackTrace();}
and here is the output:
F:\java rs_compare
not ok
oracle.jdbc.driver.OracleResultSetImpl@4413ee
oracle.jdbc.driver.OracleResultSetImpl@786e64
as you can see the resultsets are different though the data they contain have to be the same.
so the 'if(resultset#1 == resultset#2)' does not work.
thanks for any help
best regards
5ithl0rdDon't cross-post.
I'll bet ResultSet implementations don't override equals() to provide "deep equals" behavior, in which case it'll be no different than using "==".
It's a bad idea to compare two ResultSets this way. You'll have to load both into objects or data structures and compare those in a "deep" way.
Besides, the ONLY way two ResultSets could be different, given the same query, would be if there were multiple clients that could write to the table between queries and change the underlying data. If your two queries are sufficiently isolated, I'd say that the same query will return the same ResultSet.
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Hi Everybody,
Can anybody tell me is there any method to compare the contents of two ResultSets and decide whether they are same or not.
ThanksYes,
Create a method that takes the two result sets, get the metada of the table and compare field by fiel.
Another alternative is to copy the ResultSet to a Vector and than compare it.
HTH
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Attachments:
TraceTest.vi 19 KBIt is only recording the last point saved from the comparison. Try This:
Message Edited by Tom Haggerty on 12-04-2007 08:50 AM
Message Edited by Tom Haggerty on 12-04-2007 08:51 AM
Sorry about the hidden wires! I just added the FOR loop very quickly and didn't clean it up.
Tom
Message Edited by Tom Haggerty on 12-04-2007 08:52 AM
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fix.PNG 11 KB -
Comparing dates for equality using API
Hello,
I was wondering if you could help me understand if it is possible for me to compare two dates for equality.
I am looking to only compare the date and the month. So, if I am checking "today" with another objects Date for equality, it obviously fails because the compareTo and the equals method of both Date and Calendar, I think, are comparing even the timestamps.
here is something I wrote for testing, which obviously is of no use
Calendar today = Calendar.getInstance();
Calendar later = Calendar.getInstance();
later.set(Calendar.HOUR, 03);
System.out.println(today.getTime());
System.out.println(later.getTime());
if(today.equals(later)){
System.out.println("BIG BANG");
if(today.compareTo(later)<0)
System.out.println("Today Date is Lesser than my Date");
else if(today.compareTo(later)>0)
System.out.println("Today Date is Greater than my date");
else
System.out.println("Both Dates are equal");
Date today = new Date();
Date myDate = new Date();
myDate.setHours(23);
System.out.println(today);
System.out.println(myDate);
if(today.compareTo(myDate)<0)
System.out.println("Today Date is Lesser than my Date");
else if(today.compareTo(myDate)>0)
System.out.println("Today Date is Greater than my date");
else
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So is then the only way left, is using the simple date formatter and going about things ?package forums;
import java.util.Calendar;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
public class CalendarExample
private static final DateFormat DF = new SimpleDateFormat("yyyy-MM-dd");
public static void main(String[] args) {
Calendar today = Calendar.getInstance();
Calendar later = Calendar.getInstance();
later.set(Calendar.HOUR, 3);
System.out.println("today="+DF.format(today.getTime()));
System.out.println("later="+DF.format(later.getTime()));
System.out.println("isSameDayAndMonth(today, later) = "+isSameDayAndMonth(today, later));
System.out.println("\n");
Calendar tomorrow = Calendar.getInstance();
tomorrow.set(Calendar.DATE, tomorrow.get(Calendar.DATE)+1);
System.out.println("today="+DF.format(today.getTime()));
System.out.println("tomorrow="+DF.format(tomorrow.getTime()));
System.out.println("isSameDayAndMonth(today, tomorrow) = "+isSameDayAndMonth(today, tomorrow));
System.out.println("\n");
public static boolean isSameDayAndMonth(Calendar a, Calendar b) {
return a.get(Calendar.DATE) == b.get(Calendar.DATE)
&& a.get(Calendar.MONTH) == b.get(Calendar.MONTH)
}You're welcome... Javas standard date libraries leave a lot be desired. I recommend you try Joda, which is [a long standing JSR, which has never gotten up|http://www.theserverside.com/news/thread.tss?thread_id=44248]. -
Compare tables in two schemas for the table with particular column & value
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Edited by: kumar73 on 29 Nov, 2012 1:50 PMHi, Kumar,
This is the SQL and PL/SQL forum. If you have a question about SQL Developer, then the SQL Developer is a better place to post it. Mark this thread as "Answered" before starting another thread for the same question.
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No question. Just a comment with code example.
Yesterday I was having issues comparing two Calendar dates. They looked equal in my println statement, but they failed the test. The solution evaded my cafeine intensified brain for hours. Then it hit me. Print out the time in milliseconds and see if the numbers were the same. Nope. Why?
The problem was that in the real world, you get dates from all over the place, not just cooked up for a text book example. (Don't you just hate those text book examples in their unrealistic world?) Anyway, I was getting a date from an HTML form and a data from a database and comparing the two once I had converted them both to a Calendar object. This seemed a reasonable choice.
Well, the java.sql.Date that the Oracle driver returned which was converted to a java.util.Date was fine. I ran this into a Calendar with the call calS.setTime(dbDate). The form date was split into fields and put into a difference Calendar obj with the call calF.set(fYear, fMonth, fDay, 0, 0, 0). This too seemed reasonable. Then a call to calS.equls(calF) resulted in a false even though the actual dates were in fact the same.
The problem was with the time. The java.sql.Date (calS) had a time of 00:00:00 which was fine. The calendar from the form also had 00:00:00 for a time since I initialized it with zeros. Hummmmm. Now what? As mentioned before, I decided to print out the actuall time in milliseconds and that gave me my answer. The two calendars were off by only milliseconds, but that's why. You see, the equals method of Calendar compares two dates/time in milliseconds. You can see this in the source for yourself. It's not difficult to read at all. Download and open the api source file, src.zip, and locate Calendar.java in the java.util directory.
The fix was to add calF.set(Calendar.MILLISECOND, 0) and calS.set(Calendar.MILLISECOND, 0) to zero out the milliseconds in each Calendar object. That did the trick. Here's example code of the problem (test1) and the solution (test2). I tried to simulate as close to real world as possible. If you have a better solution or I've made some error, please let me know. I'm always looking for better ways.
Main.java
import java.util.Calendar;
import java.util.Date;
import java.text.SimpleDateFormat;
public class Main {
private int fYear = 2003;
private int fMonth = 3; // march
private int fDay = 14;
public static void main(String[] args) {
Main main = new Main();
main.test1();
main.test2();
public void test1() {
SimpleDateFormat df = new SimpleDateFormat();
// get the date from the form
Calendar calF = Calendar.getInstance();
calF.set(fYear, fMonth-1, fDay, 0, 0, 0); // month starts at 0 - so march would be 2
System.out.println("From form date: [" + df.format(calF.getTime()) + "] [" + calF.getTimeInMillis() + "]");
// simulate other activity in the app
try {
Thread.sleep(5000);
catch (Exception ex) {
ex.printStackTrace();
// get the Date from the shared object which comes from a database (java.sql.Date)
// the return is java.util.Date
// convert to a Calendar
SharedObject so = new SharedObject();
Date myDate = so.getTheDate();
Calendar calS = Calendar.getInstance();
calS.setTime(myDate);
System.out.println("Shared Object date: [" + df.format(calS.getTime()) + "] [" + calS.getTimeInMillis() + "]");
// compare the two calendars for equality
if (calS.equals(calF)) {
System.out.println("The same");
else {
System.out.println("NOT the same");
public void test2() {
SimpleDateFormat df = new SimpleDateFormat();
// get the date from the form
Calendar calF = Calendar.getInstance();
calF.set(fYear, fMonth-1, fDay, 0, 0, 0);
calF.set(Calendar.MILLISECOND, 0); // the magic bean
System.out.println("From form date: [" + df.format(calF.getTime()) + "] [" + calF.getTimeInMillis() + "]");
// simulate other activity in the app
try {
Thread.sleep(5000);
catch (Exception ex) {
ex.printStackTrace();
// get the Date from the shared object which comes from a database (java.sql.Date)
// the return is java.util.Date
// convert to a Calendar
SharedObject so = new SharedObject();
Date myDate = so.getTheDate();
Calendar calS = Calendar.getInstance();
calS.setTime(myDate); // just to be safe
calF.set(Calendar.MILLISECOND, 0);
System.out.println("Shared Object date: [" + df.format(calS.getTime()) + "] [" + calS.getTimeInMillis() + "]");
// compare the two calendars for equality
if (calS.equals(calF)) {
System.out.println("The same");
else {
System.out.println("NOT the same");
SharedObject.java
public class SharedObject {
public java.util.Date getTheDate() {
java.util.Date d = null;
try {
java.sql.Date s = java.sql.Date.valueOf("2003-3-14"); // this march is converted internally
d = (java.util.Date)s;
catch (Exception ex) {
ex.printStackTrace();
return d;
} The output
From form date: [3/14/03 12:00 AM] [1047621600296]
Shared Object date: [3/14/03 12:00 AM] [1047621600000]
NOT the same
From form date: [3/14/03 12:00 AM] [1047621600000]
Shared Object date: [3/14/03 12:00 AM] [1047621600000]
The sameSo your post boils down to the fact that Calendar's set(year, month, day, hour, minute, second) method doesn't change the milliseconds fraction?
Given that there is this method, I guess it would be nice if there was a method that simultaneously set all fields, but the API does state:
Previous values of other fields are retained. If this is not desired, call clear() first. -
Is it possible to compare two different layers to see if they are in fact the same image?
I'm actually working on a game at the moment. The game map was created by using game sprites created by other people. For example, I found 5 different pictures of trees, and copy pasted them into photoshop multiple times to create a forest. I have 100 trees in my photoshop document, but in reality, they are all made up of only 5 images. I want to save out each of these trees into a format usable by my game engine. I want to save each layer as an image, but avoid saving duplicates. Thus the need to compare layers for equality.
Is it possible to do this within a photoshop script? Thanks for any help you can provide.but wouldn't this only work in the instance of them being on top of each other?
That bit of code presumes:
The layers are in the same document
The layers are the only two layers visible
The content of the layers is aligned.
The layers have simple content (no layer masks, vector masks, layer styles)
There may be other assumptions that I'm making, but this is all that I can think of.
For the trees/forest problem, I would iterate though the tree-layers.
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Hide the background layer.
Copy the first layer to the new document.
Copy the second layer to the new doc
Do the layer comparison code from above my previous post
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Copy and compare the new layer against each layer in the new document.
Delete it if it's a dupe.
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Hi.
I was wondering how Oracle does comparison for equality of objects that contains parameters of user defined types.
Suppose I have an object with a parameters whose types are:
1) number,
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