单表更新：
[ WITH [ RECURSIVE ] with_query [, ...] ]
UPDATE [/*+ plan_hint */] [ ONLY ] table_name [ partition_clause ] [ * ] [ [ AS ] alias ]
SET {column_name = { expression | DEFAULT } 
    |( column_name [, ...] ) = {( { expression | DEFAULT } [, ...] ) |sub_query }}[, ...]
    [ FROM from_list] [ WHERE condition | WHERE CURRENT OF cursor_name ]
    [ ORDER BY {expression [ [ ASC | DESC | USING operator ]
    [ LIMIT { count } ]
    [ RETURNING {* 
                | {output_expression [ [ AS ] output_name ]} [, ...] }];

多表更新：
[ WITH [ RECURSIVE ] with_query [, ...] ]
UPDATE [/*+ plan_hint */] table_list
SET {column_name = { expression | DEFAULT } 
    |( column_name [, ...] ) = {( { expression | DEFAULT } [, ...] ) |sub_query }}[, ...]
    [ FROM from_list] [ WHERE condition ];

where sub_query can be:
SELECT [ ALL | DISTINCT [ ON ( expression [, ...] ) ] ]
{ * | {expression [ [ AS ] output_name ]} [, ...] }
[ FROM from_item [, ...] ]
[ WHERE condition ]
[ GROUP BY grouping_element [, ...] ]
[ HAVING condition [, ...] ]
[ ORDER BY {expression [ [ ASC | DESC | USING operator ] | nlssort_expression_clause ] [ NULLS { FIRST | LAST } ]} [, ...] ]
[ LIMIT { [offset,] count | ALL } ]