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
    )

Answer 3

另一种方法

SELECT COUNT(DISTINCT COLA || COLB)
FROM THE_TABLE

http://www.sqlfiddle.com/#!4/c287e/2

Answer 4

SELECT（从...中选择计数（可乐）），（从...中选择计数（colb））...

你可能想看看这个：

http://www.java2s.com/Code/Oracle/Aggregate-Functions/COUNTcolumnandCOUNTcountthenumberofrowspassedintothefunction.htm

如果您愿意，可以将Distinct放在子查询中。

Answer 5

在Oracle DB中，您可以连接列，然后依靠下面的连接字符串：

SELECT count(DISTINCT concat(ColumnA, ColumnB)) FROM TableX;

在MySql中，您只需在count方法中添加列作为参数。

SELECT count(DISTINCT ColumnA, ColumnB) FROM TableX;

Answer 6

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