计数2个不同的列

Question

如何获得2列的计数,以便有两列的不同组合？

Select count(distinct cola, colb)

Answer 1

SELECT  COUNT(*)
FROM    (
        SELECT  DISTINCT a, b
        FROM    mytable
        )

Answer 2

SELECT COUNT(1)
  FROM (
    SELECT DISTINCT COLA, COLB
      FROM YOUR_TABLE
    )