Single-Column Format

Use the single-column format to pair one column with a single expression.
Single-Column Format

1 + , column  = 
2.1 expression
2.1  ( singleton_select )
2.1 NULL
2.1  collection_var
Element Description Restrictions Syntax
column Column to be updated Cannot be a serial data type Identifier
collection_var Host or program variable Must be declared as a collection data type Language specific
expression Returns a value for column Cannot contain aggregate functions Expression
singleton _select Subquery that returns exactly one row Returned subquery values must have a 1-to-1 correspondence with column list SELECT statement

You can use this syntax to update a column that has a ROW data type.

You can include any number of "single column = single expression" terms. The expression can be an SQL subquery (enclosed between parentheses) that returns a single row, provided that the corresponding column is of a data type that can store the value (or the set of values) from the row that the subquery returns.

To specify values of a ROW-type column in a SET clause, see Updating ROW-Type Columns. The following examples illustrate the single-column format of the SET clause. 
UPDATE customer
   SET address1 = '1111 Alder Court', city = 'Palo Alto',
      zipcode = '94301' WHERE customer_num = 103;

UPDATE stock
   SET unit_price = unit_price * 1.07;