A Top-N query is used to retrieve the top or bottom N rows from an ordered set. Combining two Top-N queries gives you the ability to page through an ordered set.
The syntax for the row limiting clause looks like below :-
[ OFFSET offset { ROW | ROWS } ]
[ FETCH { FIRST | NEXT } [ { rowcount | percent PERCENT } ]
{ ROW | ROWS } { ONLY | WITH TIES } ]SQL> select * from emp;
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
7839 KING PRESIDENT 17-NOV-81 5000 10
7698 BLAKE MANAGER 7839 01-MAY-81 2850 30
7782 CLARK MANAGER 7839 09-JUN-81 2450 10
7566 JONES MANAGER 7839 02-APR-81 2975 20
7788 SCOTT ANALYST 7566 19-APR-87 3000 20
7902 FORD ANALYST 7566 03-DEC-81 3000 20
7369 SMITH CLERK 7902 17-DEC-80 800 20
7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30
7521 WARD SALESMAN 7698 22-FEB-81 1250 500 30
7654 MARTIN SALESMAN 7698 28-SEP-81 1250 1400 30
7844 TURNER SALESMAN 7698 08-SEP-81 1500 0 30
7876 ADAMS CLERK 7788 23-MAY-87 1100 20
7900 JAMES CLERK 7698 03-DEC-81 950 30
7934 MILLER CLERK 7782 23-JAN-82 1300 10
14 rows selected.
/* The example below returns the 5 largest values from an ordered set. Using the ONLY clause limits the number of rows returned to the exact number requested. */
SQL> SELECT *
2 FROM emp
3 ORDER BY sal DESC
4 FETCH FIRST 5 ROWS ONLY;
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
7839 KING PRESIDENT 17-NOV-81 5000 10
7788 SCOTT ANALYST 7566 19-APR-87 3000 20
7902 FORD ANALYST 7566 03-DEC-81 3000 20
7566 JONES MANAGER 7839 02-APR-81 2975 20
7698 BLAKE MANAGER 7839 01-MAY-81 2850 30
/* The example below returns the 5 largest values from an ordered set. Using the TIES clause will allow Oracle to fetch more rows if a tie occurs. */
SQL> SELECT *
2 FROM emp
3 ORDER BY sal DESC
4 FETCH FIRST 5 ROWS WITH TIES;
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
7839 KING PRESIDENT 17-NOV-81 5000 10
7788 SCOTT ANALYST 7566 19-APR-87 3000 20
7902 FORD ANALYST 7566 03-DEC-81 3000 20
7566 JONES MANAGER 7839 02-APR-81 2975 20
7698 BLAKE MANAGER 7839 01-MAY-81 2850 30
/* The following query returns the bottom 20% of rows. */
SQL> SELECT *
2 FROM emp
3 ORDER BY sal
4 FETCH FIRST 20 PERCENT ROWS ONLY;
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
7369 SMITH CLERK 7902 17-DEC-80 800 20
7900 JAMES CLERK 7698 03-DEC-81 950 30
7876 ADAMS CLERK 7788 23-MAY-87 1100 20
SQL> SELECT *
2 FROM emp
3 ORDER BY sal
4 OFFSET 4 ROWS FETCH NEXT 4 ROWS ONLY;
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
7654 MARTIN SALESMAN 7698 28-SEP-81 1250 1400 30
7934 MILLER CLERK 7782 23-JAN-82 1300 10
7844 TURNER SALESMAN 7698 08-SEP-81 1500 0 30
7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30
SQL> SELECT *
2 FROM emp
3 ORDER BY sal
4 OFFSET 4 ROWS FETCH NEXT 20 PERCENT ROWS ONLY;
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
7521 WARD SALESMAN 7698 22-FEB-81 1250 500 30
7934 MILLER CLERK 7782 23-JAN-82 1300 10
7844 TURNER SALESMAN 7698 08-SEP-81 1500 0 30
