update_statement 
<update_statement>
::=
UPDATE [OF] <table_name>
[<reference_name>]
SET <set_update_clause>,...
[KEY <key_spec>,...]
[WHERE <search_condition>]
[NOWAIT] [IGNORE TRIGGER]
| UPDATE [OF] <table_name> [<reference_name>] (<column_name>,...)
VALUES (<extended_value_spec>,...)
[KEY <key_spec>,...]
[WHERE <search_condition>] [NOWAIT] [IGNORE
TRIGGER]
| UPDATE [OF] <table_name> [<reference_name>] SET
<set_update_clause>,...
WHERE CURRENT OF <result_table_name>
[NOWAIT]
| UPDATE [OF] <table_name> [<reference_name>]
(<column_name>,...)
VALUES (<extended_value_spec>,...) WHERE CURRENT OF
<result_table_name> [NOWAIT]