update

UPDATE()			 SQL Commands			     UPDATE()



NAME
       UPDATE - update rows of a table


SYNOPSIS
       UPDATE [ ONLY ] table SET column = { expression | DEFAULT } [, ...]
	   [ FROM fromlist ]
	   [ WHERE condition ]


DESCRIPTION
       UPDATE  changes	the  values of the specified columns in all rows that
       satisfy the condition. Only the columns to be modified  need  be	 men-
       tioned  in the statement; columns not explicitly SET retain their pre-
       vious values.

       By default, UPDATE will update rows in the specified table and all its
       subtables.  If  you  wish to only update the specific table mentioned,
       you must use the ONLY clause.

       You must have the UPDATE privilege on the table to update it, as	 well
       as  the	SELECT	privilege  to  any table whose values are read in the
       expressions or condition.

PARAMETERS
       table  The name (optionally schema-qualified) of the table to  update.

       column The name of a column in table.

       expression
	      An  expression  to assign to the column. The expression may use
	      the old values of this and other columns in the table.

       DEFAULT
	      Set the column to its default value (which will be NULL  if  no
	      specific default expression has been assigned to it).

       fromlist
	      A list of table expressions, allowing columns from other tables
	      to appear in the WHERE condition and the update expressions.

       condition
	      An expression that returns a value of type boolean.  Only	 rows
	      for which this expression returns true will be updated.

OUTPUTS
       On  successful  completion, an UPDATE command returns a command tag of
       the form

       UPDATE count

       The count is the number of rows	updated.  If  count  is	 0,  no	 rows
       matched the condition (this is not considered an error).

EXAMPLES
       Change  the  word  Drama	 to  Dramatic in the column kind of the table
       films:

       UPDATE films SET kind = ’Dramatic’ WHERE kind = ’Drama’;


       Adjust temperature entries and  reset  precipitation  to	 its  default
       value in one row of the table weather:

       UPDATE weather SET temp_lo = temp_lo+1, temp_hi = temp_lo+15, prcp = DEFAULT
	 WHERE city = ’San Francisco’ AND date = ’2003-07-03’;


COMPATIBILITY
       This  command conforms to the SQL standard. The FROM clause is a Post-
       greSQL extension.



SQL - Language Statements	  2008-01-03			     UPDATE()