IF condition expression evaluation in TSQL
In programming language like C#, java if a condition has multiple expressio开发者_如何学Gons with AND(&&) operator then the second expression is only evaluated if first expression is true.
What about in TSQL? To be specific this is a condition in a Stored procedure in Microsoft Sql server.
IF (exprA AND exprB)
In the above condition if exprA is false then will the exprB is evaluated or not?
You can't rely on SQL Server not evaluating the second expression if the first one is false. See my answer to the question linked by Martin in his comment.
As others have noted, it depends on what your IF conditions are. However, if you are only using simple expressions, it will short circuit. Run the following and you'll see that the divide-by-zero error in the second expression never occurs:
IF (1 = 0 AND (1/0) = 0)
BEGIN
PRINT 'test1'
END
ELSE
BEGIN
PRINT 'test2'
END
The CASE
statement seems to allow short-circuiting as shown in the examples below:
-- Conditional Query
select case when 1>0 and 1/0>0 then 1 else 0 end
-- Short Circuited Conditional Query
select case when -1>0 and 1/0>0 then 1 else 0 end
create proc ABCDemo1
(
@Name varchar(50),
@date varchar(50)
)
as begin
if(@Name!='' and @date='')
begin
select * from Table1 where condition1
end
else if(@Name='' and @date!='')
begin
select * from Table2 where condition2
end
else if(@Name!='' and @date!='')
begin
select * from Table3 where condition3
end
end
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