Question

I want to get the most common values for all columns in a mySQL table.

[id]  [UserID]            [UserID2]
1     johnnietheblack     marywhite
2     johnnietheblack     marywhite
3     dannyrottenegg      dannyrottenegg     
4     marywhite           marywhite
5     marywhite           johnnietheblack     
6     johnnietheblack     marywhite

Here’s the output I want:

[id]  [UserID]            [Count]
    1     johnnietheblack     4
    2     dannyrottenegg      2
    3     marywhite           6

I can use the following to get the common values for one columns. But how can I get the common values for all columns?

SELECT COUNT(*) AS `Rows`, UserID
FROM table-name
GROUP BY UserID
ORDER BY `Rows` DESC

Answer 1

SELECT UserID, COUNT(*) FROM
(SELECT UserID FROM tablename
 UNION ALL
 SELECT UserID2 FROM tablename) t
GROUP BY UserID

I didn’t include the id column because it doesn’t seem to correlate with the values.

If you want to see all of the ids for each name, you can use GROUP_CONCAT:

SELECT GROUP_CONCAT(id), UserID, COUNT(*) FROM
(SELECT id, UserID FROM tablename
 UNION ALL
 SELECT id, UserID2 FROM tablename) t
GROUP BY UserID