从另一个表更新表

Question

I want to update a field based on another table field. The table is like this:

TABLE A
SID  SMONTH  STID VID  VVID
1    201312   s10  v5    ?
2    201312   s10  v5    ?
1    201312   s11  v7    ?
2    201401   s11  v7    ?
1    201312    s1  v9    ?
2    201401    s1  v9    ?
1    201312    s1  v60   ?
1    201312    s1  v71   ?

In the above table A , i need to update VVID column with the VVID from the below table B.

TABLE B
VVID   STID  VID   WEIGHT
v1     s10   v5    0.5
v2     s10   v5    7.5
v1     s11   v7    1.5
v2     s11   v7    6.5
v1     s1    v9    5
v2     s1    v9    5
v1     s1    v60   5
v1     s1    v71   5

In the above table B , VVID is generated based on three fields STID , VID and WEIGHT . But in the table A , i dont have WEIGHT field. So if i use the below code i am getting "single row query returns more than one row" error.

UPDATE  A
SET VVID = (SELECT distinct VVID
          FROM  B
          WHERE B.STID = A.STID and B.VID = A.VID  ) 

Please give me suggestions.

Thanks Sathish

Answer 1

Here your inner query is returning more than one row as the additional criteria for comparing the weight is missing so for example STID = s10 and VID = v5 the inner query will return two rows with VVID = v1 and VVID = v2. The update clause requires a single value after SET.

You can modify your query to update the max or min of VVID if it is acceptable for your application

UPDATE A SET VVID = (SELECT MIN(VVID) FROM B WHERE B.STID = A.STID and B.VID = A.VID)

or

UPDATE A SET VVID = (SELECT MAX(VVID) FROM B WHERE B.STID = A.STID and B.VID = A.VID)

Answer 2

I think you can update with an INNER JOIN query

UPDATE A 
JOIN B
ON  B.STID = A.STID 
AND B.VID = A.VID 
SET A.VVID = B.VVID

Answer 3

Please use union with constant value instead of join. For details please refer to the post http://scn.sap.com/docs/DOC-40619