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Editorial Team
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Asked: 2026-06-02T16:07:11+00:00

I have a situation where I need to insert data from table1 to table2.

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I have a situation where I need to insert data from table1 to table2. Before insert check if a certain row already exist in the table2.

Conditions are if:
1) the values of id and ahccs are same in both the table, then don’t do anything.
2) the value of id are same but ahccs are different, then set flag =’z’ and insert the same id with the new ahccs value.

I am using SQLSERVER 2008 R2. How could I achieve this?

I might need something like this.

DECLARE @table1 TABLE 
(id int not null, ahccs int not null, info varchar(25), flag varchar(2))
DECLARE @table2 TABLE 
(id int not null, ahccs int not null, info varchar(25), flag varchar(2))

INSERT INTO @table1
VALUES(1, 1223, 'et', 'X')
INSERT INTO @table1
VALUES(2, 321, 'et', 'X')
INSERT INTO @table1
VALUES(3, 134, 'et', 'X' )
INSERT INTO @table1
VALUES(4, 168, 'et', 'X' )
INSERT INTO @table1
VALUES(5, 123, 'et', 'X' )


INSERT INTO @table2
VALUES(1, 1223, 'dt', 'y' )
INSERT INTO @table2
VALUES(2, 456, 'dt', 'y' )
INSERT INTO @table2
VALUES(3, 123, 'dt', 'y' )
INSERT INTO @table2
VALUES(4, 193, 'dt', 'y' )
--SELECT * FROM @table1

SELECT * FROM @table2



MERGE
INTO    @table2 t2
USING   @table1 t1
ON      t2.id = t1.id 
WHEN MATCHED AND t2.ahccs != t1.ahccs THEN
UPDATE
SET     flag = 'z'
INSERT VALUES (t2.id, t1.ahccs, t1.info, 'l');

The two issues I am having are:
1) Merge doesn’t support multiple steps, I believe.
2) Update is not allowed in WHEN NOT MATCHED case.

Please advise.

Thank You.

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1 Answer

  1. Editorial Team

    I think I understand the requirements now. You want to update records in table2 where the id matches but ahccs does not, setting the flag to ‘z’. Additionally, for these mismatches, a new row should be inserted into table2 with the same id but the ahccs from table1, and a flag of ‘l’.

    DECLARE @tmp TABLE (id int, ahccs int, info varchar(25), flag varchar(2))
MERGE
INTO    @table2 t2
USING   @table1 t1
ON      t2.id = t1.id
WHEN NOT MATCHED THEN
    INSERT VALUES (t1.id, t1.ahccs, t1.info, t1.flag)
WHEN MATCHED and t2.ahccs <> t1.ahccs THEN
    UPDATE SET flag = 'z'
output inserted.id, t1.ahccs, t1.info, inserted.flag
into @tmp;

insert into @table2
select id, ahccs, info, 'l' as flag
from @tmp
where flag = 'z' -- don't insert what we've already inserted
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