Question

注意：请JOIN取消。

假设我有一个表user，其字段名称为gender。 gender值可以是0，1，-1。

我想分别知道那些值的数量。我所知道的是使用三个sql查询，如下所示。

select count(1) from user where gender=0
select count(1) from user where gender=1
select count(1) from user where gender=-1

问题：如何将上述内容合并为一个查询？顺便说一句，我是SQL的新手。

Answer 1

select gender, count(*) 
from user 
group by gender

Answer 2

GROUP BY最有可能为您提供最佳服务。但是，你唯一的限制是＆＃34; NO JOIN＆＃34;。对于

中的任何一个，这将允许（除GROUP BY之外）

SELECT
  (SELECT COUNT(1) FROM User WHERE gender = 0) AS genderNought
  , (SELECT COUNT(1) FROM User WHERE gender = 1) AS genderOne
  , (SELECT COUNT(1) FROM User WHERE gender = -1) AS genderMinusOne;

和

SELECT COUNT(1) AS hits, gender, 'genderNought' AS genderInWords FROM User WHERE gender = 0 UNION ALL
SELECT COUNT(1), gender, 'genderOne' FROM User WHERE gender = 1 UNION ALL
SELECT COUNT(1), gender, 'genderMinusOne' FROM User WHERE gender = -1;

。

请参阅SQL Fiddle。

sql将多个查询合并为一个？

2 个答案: