Syntax
<alter_user_statement> ::= ALTER USER <user_name> [<user_mode>] [TIMEOUT <unsigned_integer> | TIMEOUT NULL] [COSTLIMIT <unsigned_integer> | COSTLIMIT NULL] [DEFAULT ROLE ALL [EXCEPT <role_name>] | DEFAULT ROLE NONE | DEFAULT ROLE <role_name>] [[NOT] EXCLUSIVE] [DEFAULTCODE <ascii_or_unicode>] [<connect_mode>]