Sams Teach Yourself SQL in 21 Days, Fourth Edition

Modifying Existing Data with the UPDATE Statement

The purpose of the UPDATE statement is to change the values of existing records. The syntax is

UPDATE table_name
SET columnname1 = value1
[, columname2 = value2]...
WHERE search_condition

This statement checks the WHERE clause first. For all records in the given table in which the WHERE clause evaluates to TRUE, the corresponding value is updated.

Example 11.4

This example illustrates the use of the UPDATE statement:

SQL> UPDATE COLLECTION
  2  SET WORTH = 900
  3  WHERE ITEM = 'STRING';

1 row updated.

To confirm the change, the query

SQL> SELECT * FROM COLLECTION
  2  WHERE ITEM = 'STRING';
						

yields ...