db2: update multiple rows and field with a select on a different table

问题

is it possible to increment the field a and b of a table (A.a and A.b) using the value c and d of a different table (B.c B.d) for all the row of A where A.x == B.z?

I'm getting crazy with this query

回答1:

DB2 and the SQL standard don't have a FROM clause in an UPDATE statement. So you have to clearly separate the steps to

identify the rows to be modified and to
compute the new value.

Here is an example:

UPDATE TABLE A
SET A.FLD_SUPV = ( SELECT B.FLD_SUPV
FROM TABLEA A, TABLEB B, TABLEC C,TABLED D
WHERE A.FLD1= B.FLD1
AND A.FLD_DT >= B.FLD_FM_DT
AND A.FLD_DT <= B.FLD_THRU_DT
AND A.FLD_DT > D.FLD_THRU_DT
AND A.FLD_DT < C.FLD_EFF_DT )
WHERE EXISTS ( SELECT B.FLD_SUPV
FROM TABLEA A, TABLEB B, TABLEC C,TABLED D
WHERE A.FLD1= B.FLD1
AND A.FLD_DT >= B.FLD_FM_DT
AND A.FLD_DT <= B.FLD_THRU_DT
AND A.FLD_DT > D.FLD_THRU_DT
AND A.FLD_DT < C.FLD_EFF_DT )

To update two fields you may use an example like this:

UPDATE table1 t1 
 SET (col1, col2) = (
  SELECT col3, col4 
  FROM  table2 t2 
  WHERE t1.col8=t2.col9
 )

The optimizer will see that the sub-queries in the SET and the FROM clause are identical and it should merge them in the internal execution plan.

回答2:

Yes it is possible. You can try something like this:

MERGE INTO A
USING (SELECT c, d, z from B) B
ON (A.x = B.z)
WHEN MATCHED THEN
UPDATE SET A.a = A.a + B.c, A.b = A.b + B.d;

You can read more about MERGE here.

回答3:

Tested under DB2 10.6

Practically the same as @jhnwsk, but with added table short cuts.

Merge into "PRODUCTION"."COUNTRY" as N
      using (SELECT OD.NAME,OD.KEY from "DEVELOPMENT"."COUNTRY" as OD) as O
      on (O.KEY = N.KEY)
      WHEN MATCHED THEN
           UPDATE SET N.NAME=O.NAME;

回答4:

This one also works quite good

update TableA A set a = (select a from TableB B where A.x = B.z) where exists (select 1 from TableB B where A.x = B.z) ;

回答5:

UPDATE CS70P t1 
 SET (T1.TIPOCRE) = (
  SELECT MOROSO
  FROM  FCSALDOC t2 ,CS70P t1
  WHERE t1.NUMCRE =t2.CODCTA
 )

来源：https://stackoverflow.com/questions/8478197/db2-update-multiple-rows-and-field-with-a-select-on-a-different-table

标签

sql

db2