SQL中如何把一个表中的字段值用另外一表中相应字段的值来替换

表C                   表D
id code specification id code specification
1 001 AAA             1 002 ABC
2 002 BBB
3 003 CCC
要求将表C修改为
id code specification id code specification
1 001 AAA              1 002 ABC
2 002 ABC
3 003 CCC

select * from C where C.code in (select D.code from D)

UPDATE C SET specification= D.specification FROM C, D
WHERE D.CODE = C.CODE