SQL: How do I SELECT only the rows with a unique value on certain column?

Question

Thanks a million everyone for everyone's response. Unfortunately, none of the solutions appear to be working on my end, and my guess is that the example I've provided is messed up.

So let me try again.

My table looks like this:

 contract project activity
row1 1000 8000 10
row2 1000 8000 20
row3 1000 8001 10
row4 2000 9000 49
row5 2000 9001 49
row6 3000 9000 79
row7 3000 9000 78

Basically, the query I'm looking for would return "2000,49" for "contract, activity" because only contract #2000 has one, and ONLY one, unique activity value.

Again, thanks a million in advance, boroatel

Answer 1

Updated to use your newly provided data:

The solutions using the original data may be found at the end of this answer.

Using your new data:

DECLARE  @T TABLE( [contract] INT, project INT, activity INT )
INSERT INTO @T VALUES( 1000,    8000,    10 )
INSERT INTO @T VALUES( 1000,    8000,    20 )
INSERT INTO @T VALUES( 1000,    8001,    10 )
INSERT INTO @T VALUES( 2000,    9000,    49 )
INSERT INTO @T VALUES( 2000,    9001,    49 )
INSERT INTO @T VALUES( 3000,    9000,    79 )
INSERT INTO @T VALUES( 3000,    9000,    78 )

SELECT DISTINCT [contract], activity FROM @T AS A WHERE
 (SELECT COUNT( DISTINCT activity ) 
  FROM @T AS B WHERE B.[contract] = A.[contract]) = 1

returns: 2000, 49

Solutions using original data

WARNING: The following solutions use the data previously given in the question and may not make sense for the current question. I have left them attached for completeness only.

SELECT Col1, Count( col1 ) AS count FROM table 
GROUP BY col1
HAVING count > 1

This should get you a list of all the values in col1 that are not distinct. You can place this in a table var or temp table and join against it.

Here is an example using a sub-query:

DECLARE @t TABLE( col1 VARCHAR(1), col2 VARCHAR(1), col3 VARCHAR(1) )

INSERT INTO @t VALUES( 'A', 'B', 'C' );
INSERT INTO @t VALUES( 'D', 'E', 'F' );
INSERT INTO @t VALUES( 'A', 'J', 'K' );
INSERT INTO @t VALUES( 'G', 'H', 'H' );

SELECT * FROM @t

SELECT col1, col2 FROM @t WHERE col1 NOT IN 
    (SELECT col1 FROM @t AS t GROUP BY col1 HAVING COUNT( col1 ) > 1)

This returns:

D   E
G   H

And another method that users a temp table and join:

DECLARE @t TABLE( col1 VARCHAR(1), col2 VARCHAR(1), col3 VARCHAR(1) )

INSERT INTO @t VALUES( 'A', 'B', 'C' );
INSERT INTO @t VALUES( 'D', 'E', 'F' );
INSERT INTO @t VALUES( 'A', 'J', 'K' );
INSERT INTO @t VALUES( 'G', 'H', 'H' );

SELECT * FROM @t

DROP TABLE #temp_table 
SELECT col1 INTO #temp_table
 FROM @t AS t GROUP BY col1 HAVING COUNT( col1 ) = 1

SELECT t.col1, t.col2 FROM @t AS t
 INNER JOIN #temp_table AS tt ON t.col1 = tt.col1

Also returns:

D   E
G   H

Answer 2

For MySQL:

SELECT contract, activity
FROM table
GROUP BY contract
HAVING COUNT(DISTINCT activity) = 1

Answer 3

Modified!

SELECT distinct contract, activity from @t a
WHERE (SELECT COUNT(DISTINCT activity) FROM @t b WHERE b.contract = a.contract) = 1

And here's another one -- shorter/cleaner without subquery

select contract, max(activity) from @t
group by contract
having count(distinct activity) = 1

Answer 4

Try this:

select 
         contract,
        max (activity) 
from
         mytable 
group by
         contract 
having
         count (activity) = 1

Answer 5

Assuming your table of data is called ProjectInfo:

SELECT DISTINCT Contract, Activity
    FROM ProjectInfo
    WHERE Contract = (SELECT Contract
                          FROM (SELECT DISTINCT Contract, Activity
                                    FROM ProjectInfo) AS ContractActivities
                          GROUP BY Contract
                          HAVING COUNT(*) = 1);

The innermost query identifies the contracts and the activities. The next level of the query (the middle one) identifies the contracts where there is just one activity. The outermost query then pulls the contract and activity from the ProjectInfo table for the contracts that have a single activity.

Tested using IBM Informix Dynamic Server 11.50 - should work elsewhere too.

Answer 6

Here is another option using sql servers count distinct:

DECLARE  @T TABLE( [contract] INT, project INT, activity INT )
INSERT INTO @T VALUES( 1000,    8000,    10 )
INSERT INTO @T VALUES( 1000,    8000,    20 )
INSERT INTO @T VALUES( 1000,    8001,    10 )
INSERT INTO @T VALUES( 2000,    9000,    49 )
INSERT INTO @T VALUES( 2000,    9001,    49 )
INSERT INTO @T VALUES( 3000,    9000,    79 )
INSERT INTO @T VALUES( 3000,    9000,    78 )



SELECT DISTINCT [contract], activity FROM @T AS A WHERE
 (SELECT COUNT( DISTINCT activity ) 
  FROM @T AS B WHERE B.[contract] = A.[contract]) = 1

Answer 7

SELECT DISTINCT Contract, Activity
FROM Contract WHERE Contract IN (
SELECT Contract 
FROM Contract
GROUP BY Contract
HAVING COUNT( DISTINCT Activity ) = 1 )

Answer 8

Utilizing the "dynamic table" capability in SQL Server
(querying against a parenthesis-surrounded query),
you can return 2000, 49 w/ the following.

If your platform doesn't offer an equivalent to the "dynamic table" ANSI-extention,
you can always utilize a temp table in two-steps/statement
by inserting the results within the "dynamic table" to a temp table,
and then performing a subsequent select on the temp table.


DECLARE @T TABLE(
    [contract] INT,
    project INT,
    activity INT
)

INSERT INTO @T VALUES( 1000, 8000, 10 )
INSERT INTO @T VALUES( 1000, 8000, 20 )
INSERT INTO @T VALUES( 1000, 8001, 10 )
INSERT INTO @T VALUES( 2000, 9000, 49 )
INSERT INTO @T VALUES( 2000, 9001, 49 )
INSERT INTO @T VALUES( 3000, 9000, 79 )
INSERT INTO @T VALUES( 3000, 9000, 78 )

SELECT
     [contract]
    ,[Activity] = max (activity)
FROM
    (
        SELECT
            [contract]
            ,[Activity]
        FROM
            @T
        GROUP BY
            [contract]
            ,[Activity]
    ) t
GROUP BY
    [contract]
HAVING count (*) = 1

Answer 9

Sorry you're not using PostgreSQL...

SELECT DISTINCT ON contract, activity * FROM thetable ORDER BY contract, activity

http://www.postgresql.org/docs/8.3/static/sql-select.html#SQL-DISTINCT

Oh wait. You only want values with exactly one...

SELECT contract, activity, count() FROM thetable GROUP BY contract, activity HAVING count() = 1

Answer 10

I'm a fan of NOT EXISTS

SELECT DISTINCT contract, activity FROM table t1
WHERE NOT EXISTS (
  SELECT * FROM table t2
  WHERE t2.contract = t1.contract AND t2.activity != t1.activity
)

Answer 11

Sorry old post I know but I had the same issue, couldn't get any of the above to work for me, however I figured it out.

This worked for me:

SELECT DISTINCT [column]As UniqueValues FROM [db].[dbo].[table]