WHERE

The WHERE clause is an optional part of an  UPDATE statement.

The WHERE clause lets you select rows based on a Boolean expression. Only rows for which the expression evaluates to TRUE are selected to return or operate upon (delete or update).

Syntax

BooleanExpression

A Boolean expression. For more information, see the Boolean Expressions topic.

Example

   -- find the flights where no business-class seats have been booked
SELECT *
  FROM FlightAvailability
  WHERE business_seats_taken IS NULL
     OR business_seats_taken = 0;

   -- Join the EMP_ACT and EMPLOYEE tables
   -- select all the columns from the EMP_ACT table and
   -- add the employee's surname (LASTNAME) from the EMPLOYEE table
   -- to each row of the result.
SELECT SAMP.EMP_ACT.*, LASTNAME
  FROM SAMP.EMP_ACT, SAMP.EMPLOYEE
  WHERE EMP_ACT.EMPNO = EMPLOYEE.EMPNO;


   -- Determine the employee number and salary of sales representatives
   -- along with the average salary and head count of their departments.
   -- This query must first create a new-column-name specified in the AS clause
   -- which is outside the fullselect (DINFO)
   -- in order to get the AVGSALARY and EMPCOUNT columns,
   -- as well as the DEPTNO column that is used in the WHERE clause
SELECT THIS_EMP.EMPNO, THIS_EMP.SALARY, DINFO.AVGSALARY, DINFO.EMPCOUNT
  FROM EMPLOYEE THIS_EMP,
     (SELECT OTHERS.WORKDEPT AS DEPTNO,
           AVG(OTHERS.SALARY) AS AVGSALARY,
           COUNT(*) AS EMPCOUNT
        FROM EMPLOYEE OTHERS
        GROUP BY OTHERS.WORKDEPT
      )AS DINFO
  WHERE THIS_EMP.JOB = 'SALESREP'
    AND THIS_EMP.WORKDEPT = DINFO.DEPTNO;

See Also