SQL查询:如何用"是"或"否"确认？

Question

我必须这样做:检查(在电影数据库中)是否有任何"喜剧".如果有一个或多个返回"是",否则返回"否".我不知道如何在选择中表达"是"和"否".提前致谢!!!

Answer 1

一种方法是使用CASE声明:

SELECT 
CASE WHEN EXISTS (SELECT NULL FROM Movies WHERE type = 'Comedy' )
THEN 'YES'
ELSE 'NO' 
END AS answer

或者,没有CASE或IF:

SELECT TOP 1 Answer
FROM
(
  SELECT 0 AS OrderBy, 'YES' AS Answer FROM Movies WHERE type = 'Comedy'
  UNION ALL
  SELECT 1, 'NO' 
)
ORDER BY OrderBy