I am a beginner in Sql server, I am doubtful about the following code:
declare @var nvarchar(50) = null
declare @bool bit
if (@var = null)
set @bool = 1
else
set @bool = 0
print @bool
The variable @bool returns as 0 , even though I declare the variable @var to be null.
Would not it be to return as 1 ?
This is one of the most particular subtleties of working with database.
This:
if (@var = null) -- Preste atenção aqui
set @bool = 1
else
set @bool = 0
It's different than this:
if (@var is null) -- Preste atenção aqui
set @bool = 1
else
set @bool = 0
The = null comparison on databases will always be false. This is because null is the absence of value , then is not comparable, unlike checking that the value is null , which causes the return to be 1 .
You will not be able to compare a null field value with the = operator, so there is IS NULL
if (@var is null)
set @bool = 1
else
set @bool = 0
There is one thing also that you have to watch your variable @var may still have an Empty value where you could check as follows.
IF (@var IS NOT NULL) OR (LEN(@var) > 0)
set @bool = 1
else
set @bool = 0