SQL, count in multiple columns then group by

Question

I am trying to count in multiple columns then group by for a total sum where the same data appears in any column

Source data table:

P1  P2  P3
-----------
a   b   
a   a   a
b   c   
a   b   b
b   a

I want it to show something like this:

Desired query output:

     Total
   -------------
a |    6
b |    5
c |    1

Answer 1

You can use a union query

SELECT x.f1,Count(x.f1) FROM
(SELECT p1 As F1 FROM table
 UNION ALL
 SELECT p2 As F1 FROM table
 UNION ALL
 SELECT p3 As F1 FROM table) x
GROUP BY x.f1