'A'，'B'和'A或B'的T-SQL COUNT

Question

从概念上讲，我有一个包含水果项目列表的表。我想通过一个查询来查看有多少苹果，橙子，“苹果或橙子”和“其他水果”。

如何在T-SQL中实现这一点？

Answer 1

SELECT 
    COUNT(*) AS Allfruits, 
    COUNT(CASE WHEN fruit = 'Apple' THEN 1 END) AS AppleCount, 
    COUNT(CASE WHEN fruit = 'Orange' THEN 1 END) AS OrangeCount, 
    COUNT(CASE WHEN fruit IN ('Apple','Orange') THEN 1 END) AS AppleOrOrangeCount, 
    COUNT(*) - COUNT(CASE WHEN fruit IN ('Apple','Orange') THEN 1 END) AS OtherFruitCount 
FROM 
    MyTable 

注：如果没有ELSE子句或某些显式条件，CASE会给出NULL。 COUNT忽略NULL。