Sybase stored Procedure Issues

Q: Sybase stored procedures, why execution to this sentence is not executed

select @nSerialNo = serialno from schedule where phonenum= @strPhoneNum and type = @nType
if @@rowcount = 0
begin
...
end
else
begin
...
end

The select result above is an empty recordset, which is returned when the stored procedure executes to an empty recordset.

Answer: If exists (select @nSerialNo = Serialno from schedule where phonenum= @strPhoneNum and type = @nType) is there a problem with the logic of this statement?

If exists is typically used to determine if a similar record exists? Now you're going to assign the results of your existence? In fact, it's better to write if exists (select 1 from Schedule where phonenum= @strPhoneNum and type = @nType)

Determine if there is such a record, and perform the appropriate processing.