SQL query to fetch rows which are not same for a given group

Question

For example for a table as below

c1      c2      c3
a       b       1
a       b       2
c       d       1
c       d       1
e       f       3
e       f       3
e       f       3
x       y       5

In this scenario I want the group value of c1, c2 where all at least one of the c3 is not same. So in this case (a, b) as one row of (a, b) is 1 and another row of (a, b) is 2.

Also row (x, y) must not be reported.

Answer 1

SELECT  c1, c2
FROM    tableName
GROUP   BY c1, c2
HAVING  COUNT(DISTINCT c3) > 1

• SQLFiddle Demo

OUTPUT

╔════╦════╗
║ C1 ║ C2 ║
╠════╬════╣
║ a  ║ b  ║
╚════╩════╝

but of you want to get all the rows with all its columns

SELECT  a.*
FROM    tableName a
        INNER JOIN
        (
            SELECT  c1, c2
            FROM    tableName
            GROUP   BY c1, c2
            HAVING  COUNT(DISTINCT c3) > 1
        ) b ON  a.c1 = b.c1 AND 
                a.c2 = b.c2

• SQLFiddle Demo

OUTPUT

╔════╦════╦════╗
║ C1 ║ C2 ║ C3 ║
╠════╬════╬════╣
║ a  ║ b  ║  1 ║
║ a  ║ b  ║  2 ║
╚════╩════╩════╝

Answer 2

Use EXISTS :

SELECT c1, c2, c3
FROM dbo.TableName t1
WHERE EXISTS
(
    SELECT 1 FROM dbo.TableName t2
    WHERE t1.c1 = t2.c1 AND t1.c2 = t2.c2
    AND   t1.c3 <> t2.c3
)

Demo (if you just want one record, use t1.c3 < t2.c3 )

Answer 3

Edit: BAsed on single pairs not being included:

If you want to get each pair, C1,C2, for which every value of C3 is different, the following will do it:

SELECT
    C1,
    C2
FROM
    dbo.Table1
GROUP BY
    C1,
    C2
HAVING
    COUNT(1) = COUNT(DISTINCT C3)
AND COUNT(1) > 1