======
UPDATE
======

Update rows of a table.

Synopsis
========

.. code-block:: sql

   UPDATE table_ident SET
       { column_ident = expression |
         ( column_ident [, ...] ) = ( expression [, ...] )
       } [, ...]
     [ 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
mentioned in the SET clause; columns not explicitly modified retain
their previous values.

Parameters
----------

:table_ident: The identifier (optionally schema-qualified) of an
    existing table.

:column_ident: The name of a column in the table identified by
    table_ident. Subfields can also be defined by using the subscript
    notation with square brackets.

:expression: An expression to assign to the column.

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