How To Use Existing Values in UPDATE Statements?

Answer 1

If a row matches the WHERE clause in a UPDATE statement, existing values in this row can be used in expressions to provide new values in the SET clause. Existing values are represented by columns in the expressions. The tutorial exercise below shows a good example:

UPDATE temp_links SET id = 1000 + id, counts = id*2
  WHERE id >= 250;
3 rows updated.

SELECT * FROM temp_links WHERE id >= 250;
   ID URL                  NOTES         COUNTS CREATED
----- -------------------- ------------ ------- ---------
 1250 Retail Sales.com     Wrong URL        500 07-MAY-06
 1260 Recruiting.com       Wrong URL        520 07-MAY-06
 1270 Payroll.com          Wrong URL        540 07-MAY-06

This statement increased values in the id column by 1000.