Question

I wrote following stored procedure in SQL Server 2005 and I get error message:

Msg 102, Level 15, State 1, Procedure sp_InsertCustTrans, Line 12
Incorrect syntax near ‘@TrID’.

My stored procedure is:

ALTER PROCEDURE [dbo].[sp_InsertCustTrans] 
-- Add the parameters for the stored procedure here
@CuID int, @TrType nvarchar(10), @TrAmt int
AS
BEGIN
SET NOCOUNT ON;
    declare @TrID int;
    Select @TrID = MAX(TransactionID) from CustTrans;
    if Isnull(@TrID)
        @TrID = @TrID + 1
    else
        @TrID = 1

-- Insert statements for procedure here
if (@TrType = 'Deposit')
    begin
        INSERT INTO CustTrans (TransactionID, TransactionDate, CustID, TransactonType, CreditAmount)
            Values(@TrID, GetDate(), @CuID, @TrType, @TrAmt);
    end
else
    begin
        INSERT INTO CustTrans (TransactionID, TransactionDate, CustID, TransactonType, DebitAmount)
            Values(@TrID, GetDate(), @CuID, @TrType, @TrAmt);
    end
END
GO

Answer 1

All assignment operations must be preceded by the keyword set.

Set @TrID = @TrID + 1

Also you are using IsNull incorrectly as Ivan points out.
The proper usage is:

If @TrID Is Null