Remove and Identify Duplicate Records in SQL - sql

Question

I have some sample records below that I need to use the CASE WHEN statement to remove and identify the duplicate records in SQL.
Quantity Values Desc event ID
1 5 Blue 12550 577
1 5 bluee 12550 525
2 10 blu 12550 535
i would like to use a case statement to show the duplicate indicators such as:
Dup_Quantity Dup_Value Dup_Desc Quantity Values Desc event ID
Y Y N 1 5 Blue 12550 577
Y Y N 1 5 Bluee 12550 525
however, after using this script, the result still shows as:
Dup_Quantity Dup_Value Dup_Desc Quantity Values Desc event ID
Y Y N 1 5 Blue 12550 577
Y Y N 1 5 Bluee 12550 525
Y N N 2 10 Blu 12550 535
SELECT DISTINCT
CASE WHEN a.Quantity = b.Quantity THEN 'Y' ELSE 'N' END AS "Dup_Quantity",
CASE WHEN a.Values = b.Values THEN 'Y' ELSE 'N' END AS "Dup_Value",
CASE WHEN a.Desc = b.Desc THEN 'Y' ELSE 'N' END AS "Dup_Desc"
FROM Table1 a
INNER JOIN Table1 b ON a.event = b.event
WHERE (a.Quantity = b.Quantity OR a.Values = b.Values OR a.Desc = b.Desc)
AND a.ID <> b.ID
Basically, record with ID 535 stills shows up in the result. Would someone Please give me some pointers?

Answer 1

SQL Fiddle
MS SQL Server 2012 Schema Setup:
CREATE TABLE Table1
([Quantity] int, [Values] int, [Desc] varchar(5), [event] int, [ID] int)
;
INSERT INTO Table1
([Quantity], [Values], [Desc], [event], [ID])
VALUES
(1, 5, 'Blue', 12550, 577),
(1, 5, 'bluee', 12550, 525),
(2, 10, 'blu', 12550, 535)
;
Query 1:
SELECT
CASE WHEN (SELECT COUNT(*)
FROM Table1 t2
WHERE t1.Quantity = t2.Quantity AND
t1.ID <> t2.ID AND t1.event = t2.event) > 0
THEN 'Y' ELSE 'N' END AS Dup_Quantity,
CASE WHEN (SELECT COUNT(*)
FROM Table1 t2
WHERE t1."Values" = t2."Values" AND
t1.ID <> t2.ID AND t1.event = t2.event) > 0
THEN 'Y' ELSE 'N' END AS Dup_Value,
CASE WHEN (SELECT COUNT(*)
FROM Table1 t2
WHERE t1."Desc" = t2."Desc" AND
t1.ID <> t2.ID AND t1.event = t2.event) > 0
THEN 'Y' ELSE 'N' END AS Dup_Desc,
*
FROM Table1 t1
WHERE
(SELECT COUNT(*)
FROM Table1 t2
WHERE t1.Quantity = t2.Quantity AND
t1.ID <> t2.ID AND t1.event = t2.event) > 0
OR
(SELECT COUNT(*)
FROM Table1 t2
WHERE t1."Values" = t2."Values" AND
t1.ID <> t2.ID AND t1.event = t2.event) > 0
OR
(SELECT COUNT(*)
FROM Table1 t2
WHERE t1."Desc" = t2."Desc" AND
t1.ID <> t2.ID AND t1.event = t2.event) > 0
Results:
| DUP_QUANTITY | DUP_VALUE | DUP_DESC | QUANTITY | VALUES | DESC | EVENT | ID |
|--------------|-----------|----------|----------|--------|-------|-------|-----|
| Y | Y | N | 1 | 5 | Blue | 12550 | 577 |
| Y | Y | N | 1 | 5 | bluee | 12550 | 525 |

Answer 2

Your query returns:
Dup_Quantity Dup_Value Dup_Desc
Y Y N
However I don't get what you want to do here, the correct version of it is:
SELECT
CASE WHEN a."Quantity" = b."Quantity" THEN 'Y' ELSE 'N' END AS "Dup_Quantity",
CASE WHEN a."Values" = b."Values" THEN 'Y' ELSE 'N' END AS "Dup_Value",
CASE WHEN a."Desc" = b."Desc" THEN 'Y' ELSE 'N' END AS "Dup_Desc",
a.*
FROM Table1 a
INNER JOIN Table1 b ON b.event = a.event
WHERE (a."Quantity" = b."Quantity" OR a."Values" = b."Values" OR a."Desc" = b."Desc")
AND a.ID <> b.ID
If you want to get duplicated rows in terms of Quantity, Values and Desc:
SELECT
a.*
FROM Table1 a
INNER JOIN Table1 b ON b.event = a.event
WHERE (a."Quantity" = b."Quantity" AND a."Values" = b."Values" AND a."Desc" = b."Desc")
AND a.ID <> b.ID