SQL Process Control Statements

If-else keywords

IF (condition)

Statement or statement block

ELSE

Statement or statement block

Statement or statement block with begin ... End indicates

IF (condition)

BEGIN

Statement 1

Statement 2

END

For example:

DECLARE @test INT

SET @test =1

SELECT @test =avg (score) from Stu WHERE stu.name= ' Lilu '

IF (@test =1)

PRINT @test

ELSE

BEGIN

IF exists (SELECT score from Stu WHERE stu.name= ' AA ')

BEGIN

DELETE from Stu WHERE stu.name= ' AA ' and score=99

END

INSERT into Stu VALUES (' AA ', 99)

SELECT score from Stu

WHERE name= ' AA '

END
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Case keyword

Case

Case

When condition 1 then result 1

When condition 2 then result 2

END

For example:

CREATE TABLE SS

(

Name varchar (10),

Score Float

)

INSERT into SS values (' Small white ', 99)

INSERT into SS values (' Little black ', 77)

INSERT into SS values (' Xiao Li ', 58)

SELECT name,

Score=case

When score<60 then ' E '

When score between, and then ' D '

When score between and "C"

When score between and the then ' B '

ElSE ' A '

END

from SS

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While keyword

while (condition)

Statement or statement block

[Breake]

DECLARE @test INT

SET @test =2

while (@test <20)

BEGIN

SET @[email protected]+2

IF (@test <>7)

BEGIN

PRINT @test

IF (@test =18)

Break

END

ELSE

IF (@test =7)

CONTINUE

END

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SQL Process Control Statements