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What is the difference between ROWNUM and ROW_NUMBER ?
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From a little reading, ROWNUM is a value automatically assigned by Oracle to a rowset (prior to ORDER BY being evaluated, so don't ever ORDER BY ROWNUM or use a WHERE ROWNUM < 10 with an ORDER BY ). ROW_NUMBER() appears to be a function for assigning row numbers to a result set returned by a subquery or partition.
ROWNUM is representative of the sequence allocated to any data retrieval bunch. ROWID is the permanent identity or address of a row. ROWNUM is a temporarily assigned sequence to a row. ROWID is a 16-digit Hexadecimal number in the format BBBBBBBB.
The Oracle/PLSQL ROWNUM function returns a number that represents the order that a row is selected by Oracle from a table or joined tables. The first row has a ROWNUM of 1, the second has a ROWNUM of 2, and so on.
Rowid gives the address of rows or records. Rownum gives a count of records. Rowid is permanently stored in the database. Rownum is not stored in the database permanently. Rowid is automatically assigned with every inserted into a table.
ROWNUM is a "pseudocolumn" that assigns a number to each row returned by a query:
SQL> select rownum, ename, deptno 2 from emp; ROWNUM ENAME DEPTNO ---------- ---------- ---------- 1 SMITH 99 2 ALLEN 30 3 WARD 30 4 JONES 20 5 MARTIN 30 6 BLAKE 30 7 CLARK 10 8 SCOTT 20 9 KING 10 10 TURNER 30 11 FORD 20 12 MILLER 10 ROW_NUMBER is an analytic function that assigns a number to each row according to its ordering within a group of rows:
SQL> select ename, deptno, row_number() over (partition by deptno order by ename) rn 2 from emp; ENAME DEPTNO RN ---------- ---------- ---------- CLARK 10 1 KING 10 2 MILLER 10 3 FORD 20 1 JONES 20 2 SCOTT 20 3 ALLEN 30 1 BLAKE 30 2 MARTIN 30 3 TURNER 30 4 WARD 30 5 SMITH 99 1 If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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