User Guide

Using SQL 459
Updating data in a database
Use the UPDATE statement in SQL to update the values of a table row. Update lets you update
the fields of a specific row or all rows in the table. The UPDATE statement has the following
syntax:
UPDATE table_name
SET column_name1=value1, ... , column_nameN=valueN
[ WHERE search_condition ]
Note: There are additional options to UPDATE depending on your database. For a complete syntax
description for UPDATE, see the product documentation.
You should not attempt to update a record’s primary key field. Your database typically enforces
this restriction.
The UPDATE statement uses the optional WHERE clause, much like the SELECT statement, to
determine which table rows to modify. The following UPDATE statement updates the e-mail
address of John Smith:
UPDATE employees SET Email='[e-mail]' WHERE EmpID = 51
Be careful using UPDATE. If you omit the WHERE clause to execute the following statement:
UPDATE employees SET Email = '[e-mail]'
you update the Email field for all rows in the table.
Deleting data from a database
The DELETE statement removes rows from a table. The DELETE statement has the following
syntax:
DELETE FROM table_name
[ WHERE search_condition ]
Note: There are additional options to DELETE depending on your database. For a complete syntax
description for DELETE, see the product documentation.
You can remove all rows from a table using a statement in the form:
DELETE FROM employees
Typically, you specify a WHERE clause to the DELETE statement to delete specific rows of the
table. For example, the following statement deletes John Smith from the table:
DELETE FROM employees WHERE EmpID=51