Question

我的表格中有一个名为type的字段，其中可能有3行：1，2和3。

现在，我根本不关心3。我需要计算type = 1和type = 2的行数。我这样做有2个查询，如下：

查询1：SELECT COUNT(id) as count FROM users WHERE type='1'
问题2：SELECT COUNT(id) as count FROM users WHERE type='2'

我只能使用一个查询执行此操作吗？如果是的话，我应该，不是吗？查询将如何显示？

Answer 1

SELECT type,
       COUNT(id) AS count
  FROM users
 WHERE type IN ('1','2')
 GROUP BY type

Answer 2

SELECT type, COUNT(id) AS count
FROM users
GROUP BY type
HAVING type < 3

Answer 3

SELECT sum(case when type = '1' then 1 else 0 end) as count_for_one,
       sum(case when type = '2' then 1 else 0 end) as count_for_tow
FROM users
WHERE type IN ('1','2')

Answer 4

如果你想要单独的数字，

SELECT SUM(IF(type='1', 1, 0)), SUM(IF(type='2', 1, 0)) 
FROM users WHERE type IN ('1', '2')

我可以在一个查询中选择更多计数吗？

4 个答案: