I'm trying to create a procedure that will take the values from a temporary table, and load them into another table. The second table has a composite unique constraint across its three columns (Not including the primary key) I'm using a merge statement to try and handle the upload, and keep getting an error saying
Msg 2627, Level 14, State 1, Line 13
Violation of UNIQUE KEY constraint 'IX_table'.
Cannot insert duplicate key in object 'dbo.table'. The duplicate key value is (aaa, aaa, aaa).
I'm really confused because the whole reason I am using the merge statement is to prevent exactly this from happening. Here's the relevant portion of the procedure (With names changed, and the insertion to the temporary table changed)
create table #TempTable(Id int
, str1 varchar(3)
, str2 varchar(15)
, str3 varchar(10))
INSERT INTO #TempTable
(str1
,str2
,str3)
VALUES
('aaa','aaa','aaa'), ('bbb', 'bbb', 'bbb'), ('aaa','aaa','aaa')
MERGE dbo.table AS t
USING #TempTable AS s
ON (t.str1 = s.str1
AND t.str2 = s.str2
AND t.str3 = s.str3)
WHEN MATCHED THEN
UPDATE SET t.str1 = s.str1
WHEN NOT MATCHED THEN
INSERT (str1, str2, str3)
VALUES (s.str1, s.str2, s.str3);
drop table #TempTable
I'm really confused as to why this isn't detecting duplicates, any ideas?
Thanks in advance
Best Answer
You will get that any time your input file has duplicates. In theory the MERGE command is doing everything in a batch so if you have the same row in the input data more than once it will try to insert it into the output table more than once giving you the error. Either dedupe your input file or use a CTE at the beginning of the MERGE to take care of it for you.