sql將多個查詢合併爲一個？

Question

請注意：NO JOIN請。

比方說，我得到了一個表user，字段名稱gender。 gender值可以是0,1,-1。

我想知道那裏的數量值分別。 我知道的是使用三個SQL查詢如下。

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

問題：如何將上述內容合併爲一個查詢？ btw，我是SQL的新手。

Answer 1

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

Answer 2

GROUP BY最有可能爲您提供最好的服務。但是，您唯一的限制是「不加入」。這將允許（除GROUP BY）爲

的

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; 

一方爲好。

參見SQL Fiddle。