Question

My first attempt at a MERGE run is not throughing any errors but it is not merging the data like I want. Can anyone tell me what I am doing wrong? The point is to compair #Temp and #tblCollectionGameList and update #tblCollectionGameList so that it contains only the items inside #Temp (inserting missing items into tblCollecitonGameList and deleteing items from tblColletionGameList that are no longer in #Temp)

    CREATE TABLE #Temp
(
    CollectionID smallint NOT NULL,
    IncludedSectionID smallint NOT NULL
)

INSERT INTO #Temp (CollectionID, IncludedSectionID) VALUES(0, 0);
INSERT INTO #Temp (CollectionID, IncludedSectionID) VALUES(0, 1);

SELECT * FROM #Temp;

CREATE TABLE #tblCollectionGameList
(
    ID smallint IDENTITY(0,1) NOT NULL,
    CollectionID smallint NOT NULL,
    IncludedSectionID smallint
)

INSERT INTO #tblCollectionGameList (CollectionID, IncludedSectionID) VALUES(0,0);
INSERT INTO #tblCollectionGameList (CollectionID, INcludedSectionID) VALUES(0,2);

SELECT * FROM #tblCollectionGameList;

BEGIN TRAN

MERGE #tblCollectionGameList AS t
USING #Temp AS s
ON (t.CollectionID = s.CollectionID)
WHEN NOT MATCHED BY TARGET
    THEN
        INSERT(CollectionID, IncludedSectionID) VALUES (s.CollectionID, s.IncludedSectionID)
WHEN NOT MATCHED BY SOURCE
    THEN
        DELETE;

SELECT * FROM #tblCollectionGameList;

ROLLBACK TRAN

DROP TABLE #Temp;
DROP TABLE #tblCollectionGameList;

Answer 1

Your problem is that you’re joining on a non-unique column.

Everything has CollectionID = 1 and so everything matches – there are no rows that meet the NOT MATCHED BY TARGET criteria, and there are no rows that meet the NOT MATCHED BY SOURCE criteria.

Instead try making the CollectionID unique within a table.

INSERT INTO #Temp (CollectionID, IncludedSectionID) VALUES(0, 0);
INSERT INTO #Temp (CollectionID, IncludedSectionID) VALUES(1, 1);

INSERT INTO #tblCollectionGameList (CollectionID, IncludedSectionID) VALUES(0,0);
INSERT INTO #tblCollectionGameList (CollectionID, INcludedSectionID) VALUES(2,2);