Update

An Update statement changes the value of columns in selected rows of a table.

Grammar

UPDATE table_name SET column_name = expression

[, column_name = expression] [WHERE conditions]

table_name is the name of the table for which you want to update values.

column_name is the name of a column, the value of which is to be changed. Multiple column values can be changed in a single statement.

expression is the new value for the column. The expression can be a constant value or a subquery that returns a single value. Subqueries must be enclosed in parentheses. See “Subqueries” for complete information about subqueries.

A Where clause can be used to restrict which rows are updated. See “Where Clause” for details.

Examples

Example A

The following example changes every record that meets the conditions in the Where clause. In this case, the salary and exempt status are changed for all employees having the employee ID E10001. Because employee IDs are unique in the emp table, only one record is updated.

UPDATE emp SET salary=32000, exempt=1

WHERE emp_id = 'E10001'

Example B

The following example uses a subquery. In this example, the salary is changed to the average salary in the company for the employee having employee ID E10001.

UPDATE emp SET salary = (SELECT avg(salary) FROM emp)

WHERE emp_id = 'E10001'