update_statement ::=
UPDATE {table_reference | [THE] (subquery1)} [alias]
SET
{column_name = {sql_expression | (subquery2)}
| (column_name [, column_name]...) = (subquery3)}
[, {column_name = {sql_expression | (subquery2)}
| (column_name [, column_name]...) = (subquery3)}]...
[WHERE {search_condition | CURRENT_OF cursor_name}] [RETURNING]
[row_expression [, row_expression]... INTO
{variable_name | :host_variable_name}
[, {variable_name | :host_variable_name}]...];