比较单个表中的两列

Question

我有一个表格alpha，它包含两个A和B列。我需要找出B有多少A。

      A             B   
      1     1
      2     2
      3     3
      4     3
      5     4
      6     7

Answer 1

尝试分组：

SELECT `B`, COUNT(*) AS `Count`
FROM `Alpha` 
GROUP BY `B`

Answer 2

试试这个

SELECT COUNT( * ) AS  `Items` ,  `B` 
FROM  `alpha` 
GROUP BY  `b`