T-SQL COUNT'A'，'B'和'A或B'

Question

从概念上讲，我有一个包含水果项目列表的表格。我想在一个查询中查看有多少苹果，橙子，“苹果或橙子”以及“其他水果”的数量。

如何在T-SQL中实现这一目标？

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

注意：CASE在没有ELSE子句或某些显式条件的情况下给出NULL。 COUNT忽略NULL。