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SELECT statements used as argument of EXISTS statements should be selective

  • Maintainability
  • - Critical

Rule description

  • SELECT statements used as argument of EXISTS statements should be selective

 

Non-compliant Code Example 

SELECT TypeId, TypeName, TypeCategory
FROM Type1
WHERE EXISTS(SELECT TypeId FROM Type2)  --Non compliant code (SELECT statements used as argument of EXISTS statements is not selective)
GO

Compliant Code Example

SELECT TypeId, TypeName, TypeCategory
FROM Type1
WHERE EXISTS(SELECT TypeId FROM Type2 WHERE TYPE2.Id = Type1.Id)  --Compliant code (SELECT statements used as argument of EXISTS statements is selective)
GO
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 VETSQLRULE7