sql - Is querying for IS NULL necessary in this CASE expression?

Question

I've got this case statement:

CASE 
  WHEN SecondScriptKind_ID IS NULL THEN 0
  WHEN SecondScriptKind_ID IN (@SqlQuery, @SqlScript) THEN 1
  ELSE 0 
END

Is the WHEN SecondScriptKind_ID IS NULL necessary in this case?

Both @SqlQuery and @SqlScript are guaranteed to contain values (NOT NULL).

Answer 1

当ANSI_NULLS设置on时，没有必要：即使@SqlQuery或@SqlScript恰好是NULL，也不会将INa 匹配NULL SecondScriptKind_ID到该列表。换句话说，条件

NULL IN (NULL, 123)

评估为NULL。保持显式NULL检查的唯一原因是，如果您想为 1 返回一个不同的数字NULL，例如负 1。