The SELECT statement in exists cannot be used to assign values.

Is the following sectionCode:

If   Exists ( Select   @ Myvalue   = Myvalue From Testtable Where Condition =   ' ABC ' )
Begin
Print   @ Myvalue  
End

When debugging in SSMs, an error is reported:

Message 102 , Level 15 , Status 1 , No 3 Line
' = ' There is a syntax error nearby.

This error should be reported by the equal sign, because the following debugging is performed:

If   Exists ( Select   1   From Testtable Where Condition =   ' ABC ' )
Begin
Print   ' Succeed! '
End

There is no problem, so I am depressed. I directly run the exists content separately, and there is no problem, and there is only one result. After searching for a long time on the Internet, there was no result. It was said that exists and select into had a conflict. I don't know the specific cause.

But fortunately there is still a solution, at least I am not too stupid, the following code can achieve the same effect:

Select   @ Myvalue   = Myvalue From Testtable Where Condition =   ' ABC '
If   @ Myvalue   Is   Not   Null
Begin
Print   @ Myvalue  
End

If any expert knows the reason, give me some guidance.