How to Convert an Outer Join Select Query to MERGE in Oracle - sql

Question

How can I convert this simple Outer Join to MERGE to update FT.SS to a certain value for the selected rows:
SELECT FT.SS FROM FT_T FT LEFT OUTER JOIN DC_T DC
ON FT.ID = DC.ID AND FT.CN = DC.CN
WHERE FT.GID = 'AB' AND SS = 'C' AND FT.DEL = 'N' AND PR_S IS NULL AND EN_S IS NULL
AND (DC.ID IS NULL OR DC.SIGNED IS NULL);
It's relatively easy to do it with UPDATE:
UPDATE FT_T FTX
SET FTX.SS = 'X'
WHERE FT.GID = 'AB' AND SS = 'C' AND FT.DEL = 'N'
AND PR_S IS NULL AND EN_S IS NULL
AND (FTX.ID, FTX.CN) = (
SELECT FT.ID, FT.CN FROM FT_T FT LEFT OUTER JOIN DC_T DC
ON FT.ID = DC.ID AND FT.CN = DC.CN
WHERE FT.GID = 'AB' AND SS = 'C' AND FT.DEL = 'N' AND PR_S IS NULL AND EN_S IS NULL
AND (DC.ID IS NULL OR DC.SIGNED IS NULL)
)
But can it be done with MERGE?

Answer 1

Your merge statement would look like:
MERGE INTO ft_t tgt
USING (SELECT ft.id,
ft.cn
FROM ft_t ft
LEFT OUTER JOIN dc_t dc ON ft.id = dc.id AND ft.cn = dc.cn
WHERE ft.gid = 'AB'
AND ft.ss = 'C'
AND ft.del = 'N'
AND ft.pr_s IS NULL
AND ft.en_s IS NULL
AND (dc.id IS NULL OR dc.signed IS NULL)) src
ON (tgt.id = src.id AND tgt.cn = src.cn) -- assuming these two columns are the primary key for the ft_t table
WHEN MATCHED THEN
UPDATE SET tgt.ss = 'X';