The AS clause names or renames a column or expression that appears in a SELECT clause. Example:

SELECT FIRSTNME AS FIRST_NAME ...

Prior to DB2 V4.1, the only way to rename a column was to create a VIEW -- a cumbersome procedure.

Query coded the old way:

Produces this result:

Query coded the new way, with column renaming:

Produces this delightful result:

• Column renaming simplifies view creation:
  
  
  • DB2 V3.1 (and prior releases):

    CREATE VIEW DZ002.EMPVIEW
    (EMPNO, FIRSTNME, MONTHLY_SALARY)
    AS SELECT EMPNO, FIRSTNME, INTEGER(SALARY/12.00)
    FROM DZ002.EMP

  • DB2 V4.1:

    CREATE VIEW DZ002.EMPVIEW
    AS SELECT EMPNO, FIRSTNME,
    INTEGER(SALARY/12.00) AS MONTHLY_SALARY
    FROM DZ002.EMP

• Column renaming is also useful in select statements using UNION -- for naming results of an expression, or for applying a uniform name to a column that has different names in the subselects that are UNIONed together.