Question

Let’s say i have a simple table voting with columns

id(primaryKey),token(int),candidate(int),rank(int).

I want to extract all rows having specific rank,grouped by candidate and most importantly only with minimum count(*).
So far i have reached

SELECT candidate, count( * ) AS count
FROM voting
WHERE rank =1
AND candidate <200
GROUP BY candidate
HAVING count = min( count )

But,it is returning empty set.If i replace min(count) with actual minimum value it works properly.
I have also tried

SELECT candidate,min(count)
FROM (SELECT candidate,count(*) AS count
      FROM voting
      where rank = 1
      AND candidate < 200
      group by candidate
      order by count(*)
      ) AS temp

But this resulted in only 1 row,I have 3 rows with same min count but with different candidates.I want all these 3 rows.

Can anyone help me.The no.of rows with same minimum count(*) value will also help.

Sample is quite a big,so i am showing some dummy values

1 $sampleToken1 101 1

2 $sampleToken2 102 1

3 $sampleToken3 103 1

4 $sampleToken4 102 1

Here ,when grouped according to candidate there are 3 rows combining with count( * ) results

candidate count( * )

101              1

103              1

102              2

I want the top 2 rows to be showed i.e with count(*) = 1 or whatever is the minimum

Answer 1

Try to use this script as pattern –

-- find minimum count
SELECT MIN(cnt) INTO @min FROM (SELECT COUNT(*) cnt FROM voting GROUP BY candidate) t;

-- show records with minimum count
SELECT * FROM voting t1
  JOIN (SELECT id FROM voting GROUP BY candidate HAVING COUNT(*) = @min) t2
    ON t1.candidate = t2.candidate;