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Friday, October 28, 2011

ORACLE SQL TUTORIAL: USEFUL QUERIES




1)    To find the nth row of a table

SQL> Select *from emp where rowid = (select max(rowid) from emp where rownum <= 4);
Or
   SQL> Select *from emp where rownum <= 4 minus select *from emp where rownum <= 3;

2)    To find duplicate rows

SQL> Select *from emp where rowid in (select max(rowid) from emp group by empno,          
         ename, mgr, job, hiredate, comm, deptno, sal);
Or
 SQL> Select empno,ename,sal,job,hiredate,comm , count(*) from emp group by
         empno,ename,sal,job,hiredate,comm  having count(*) >=1;

3)    To delete duplicate rows

      SQL> Delete emp where rowid in (select max(rowid) from emp group by
              empno,ename,mgr,job,hiredate,sal,comm,deptno);

4)    To find the count of duplicate rows

      SQL> Select ename, count(*) from emp group by ename having count(*) >= 1;

5)    How to display alternative rows in a table?

          SQL> select *from emp where (rowid,0) in (select rowid,mod(rownum,2) from emp);

6)    Getting employee details of each department who is drawing maximum sal?

       SQL> select *from emp where (deptno,sal) in
             ( select deptno,max(sal)  from emp group by deptno);

7)    How to get number of employees in each department  , in which department is having more than 2500 employees?

       SQL> Select deptno,count(*) from emp group by  deptno having count(*) >2500;

8)    To reset the time to the beginning of the day


                  SQL> Select to_char(trunc(sysdate),’dd-mon-yyyy hh:mi:ss am’) from dual;


9)    To find nth maximum sal

  SQL> Select *from emp where sal in (select max(sal) from (select *from emp order by sal)
          where rownum <= 5);




3 Responses to “ORACLE SQL TUTORIAL: USEFUL QUERIES”

Michael Coughlin said...
June 18, 2012 at 11:09 AM

I have written a couple articles which you may want to link to:

This is SQL/PL/SQL related:
http://www.michaelcoughlin.net/blog/index.php/2011/09/ora-00054/

This is Apps 11i related:
http://www.michaelcoughlin.net/blog/index.php/2011/07/oracle-text-output-not-ie/

I would be happy to contribute more if desired.


Team search said...
September 14, 2012 at 11:36 AM

Hi Michael,

If you would like to share your knowledge, we welcome you as a Guest Author.

Regards,
Team Search


Sridevi K said...
October 8, 2016 at 1:14 AM

Regards
Sridevi Koduru (Senior Oracle Apps Trainer Oracleappstechnical.com)
LinkedIn profile - https://in.linkedin.com/in/sridevi-koduru-9b876a8b
Please Contact for One to One Online Training on Oracle Apps Technical, Financials, SCM, SQL, PL/SQL, D2K at training@oracleappstechnical.com | +91 - 9581017828.


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