SQL Server: How to check if the value of returned field is not null -

i have sql statement follows:

select  returndate    <joins>   <conditions> 

how check if returndate not null?

you can use case is null (or is not null):

select case           when returndate null 'it null'           else 'it not null'         end isitnull    dbo.tablename .... 

if need filter null/not null values can use is not null:

where returndate not null  ...