can not update duplicate records

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can not update duplicate records

Author

Topic

rudba
Constraint Violating Yak Guru

415 Posts

Posted - 2009-04-17 : 12:45:31

Why i can not update the duplicate records?
the output will be dup='Y' for Id: 1, and 2

declare @tbl1 table
(ID INT,
Dup nvarchar(1)
)

INSERT INTO @tbl1
SELECT 1, 'Y'

INSERT INTO @tbl1
SELECT 1, null

INSERT INTO @tbl1
SELECT 1, null

INSERT INTO @tbl1
SELECT 2, 'Y'

INSERT INTO @tbl1
SELECT 2, null

INSERT INTO @tbl1
SELECT 2, null

INSERT INTO @tbl1
SELECT 3, null

INSERT INTO @tbl1
SELECT 4, null

UPDATE a
SET a.Dup = 'Y'
FROM (
SELECT ID
FROM @tbl1
WHERE Dup = 'Y'
Group By ID
) d
join @tbl1 a
on a.ID = d.ID
WHERE a.Dup!= 'Y'

select ID,Dup from @tbl1

vijayisonly
Master Smack Fu Yak Hacker

1836 Posts

Posted - 2009-04-17 : 13:15:57

may be u need this?

UPDATE a
SET a.Dup = 'Y'
FROM (
SELECT ID,count(ID) as cnt
FROM @tbl1
Group By ID
) d
join @tbl1 a
on a.ID = d.ID
WHERE d.cnt > 1

rudba
Constraint Violating Yak Guru

415 Posts

Posted - 2009-04-17 : 13:34:35

thank vijayisonly,

if i have more data, it will update Id =4 too.

declare @tbl1 table
(ID INT,
Dup nvarchar(1)
)

INSERT INTO @tbl1
SELECT 1, 'Y'

INSERT INTO @tbl1
SELECT 1, null

INSERT INTO @tbl1
SELECT 1, null

INSERT INTO @tbl1
SELECT 2, 'Y'

INSERT INTO @tbl1
SELECT 2, null

INSERT INTO @tbl1
SELECT 2, null

INSERT INTO @tbl1
SELECT 3, null

INSERT INTO @tbl1
SELECT 4, null

INSERT INTO @tbl1
SELECT 4, null

INSERT INTO @tbl1
SELECT 4, null

INSERT INTO @tbl1
SELECT 4, null

UPDATE a
SET a.Dup = 'Y'
FROM (
SELECT ID,count(ID) as cnt
FROM @tbl1
Group By ID
) d
join @tbl1 a
on a.ID = d.ID
WHERE d.cnt > 1

select ID,Dup from @tbl1

vijayisonly
Master Smack Fu Yak Hacker

1836 Posts

Posted - 2009-04-17 : 13:36:43

If you have 3 records for ID = 4 ....Isn't that considered duplicate?

Are you saying we should be updating only if Dup = 'Y' for one of the rows?
If that is the case...try this

UPDATE a
SET a.Dup = 'Y'
FROM (
SELECT ID,Dup
FROM @tbl1
where Dup = 'Y'
) d
join @tbl1 a
on a.ID = d.ID

Lamprey
Master Smack Fu Yak Hacker

4614 Posts

Posted - 2009-04-17 : 13:49:54

Another alternative:

UPDATE @tbl1
SET Dup = 'Y'
WHERE ID IN (SELECT DISTINCT ID FROM @tbl1 WHERE Dup = 'Y')

visakh16
Very Important crosS Applying yaK Herder

52326 Posts

Posted - 2009-04-17 : 13:55:58

[code]
UPDATE t
SET t.Dup='Y'
FROM @tbl1 t
JOIN (SELECT ID FROM @tbl1 GROUP BY ID HAVING COUNT(CASE WHEN Dup='Y' THEN 1 ELSE 0 END) >0 ) t1
ON t1.ID=t.ID
WHERE t.Dup IS NULL
[/code]

rudba
Constraint Violating Yak Guru

415 Posts

Posted - 2009-04-17 : 15:12:53

thanks guys,
it works.

visakh16
Very Important crosS Applying yaK Herder

52326 Posts

Posted - 2009-04-17 : 15:15:02

welcome

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