Question

I’m having some trouble with this statement, owing no doubt to my ignorance of what is returned from this select statement:

declare @myInt as INT
set @myInt = (select COUNT(*) from myTable as count)

if(@myInt <> 0) 
begin
   print 'there's something in the table'
end

There are records in myTable, but when I run the code above the print statement is never run. Further checks show that myInt is in fact zero after the assignment above. I’m sure I’m missing something, but I assumed that a select count would return a scalar that I could use above?

Answer 1

If @myInt is zero it means no rows in the table: it would be NULL if never set at all.

COUNT will always return a row, even for no rows in a table.

Edit, Apr 2012: the rules for this are described in my answer here:Does COUNT(*) always return a result?

Your count/assign is correct but could be either way:

select @myInt = COUNT(*) from myTable
set @myInt = (select COUNT(*) from myTable)

However, if you are just looking for the existence of rows, (NOT) EXISTS is more efficient:

IF NOT EXISTS (SELECT * FROM myTable)