标量值函数不返回任何内容

Question

  

可能重复：
  SQL Stored Procedure Parameters being Corrupted?

我陷入了一个简单的SQL Server标量值函数返回0的情况。 谁能告诉我我做错了什么。

set ANSI_NULLS ON
set QUOTED_IDENTIFIER ON
go

ALTER FUNCTION [dbo].[OpeningBalance]
(
    @AccountCode AS varchar,
    @FromDate AS datetime
)
RETURNS numeric
AS
BEGIN
    DECLARE @Balance AS numeric

    SELECT     
      @Balance = SUM(Debit) - SUM(Credit)
    FROM 
    (
        SELECT     
            CASE 
               WHEN Debit - Credit > 0 THEN Debit - Credit 
               ELSE 0 
            END AS Debit, 
            CASE 
              WHEN Credit - Debit > 0 THEN Credit - Debit 
              ELSE 0 
            END AS Credit
        FROM
        (
             SELECT     
               SUM(VoucherDetail.Debit) AS Debit, 
               SUM(VoucherDetail.Credit) AS Credit
             FROM          VoucherMaster AS VoucherMaster 
             INNER JOIN VoucherDetail AS VoucherDetail 
                     ON VoucherMaster.ID = VoucherDetail.VoucherMasterID
             WHERE (VoucherDetail.AccountCode = @AccountCode) 
               AND (VoucherMaster.VoucherDate < @FromDate)
        ) AS Data
        UNION ALL
        SELECT     
          CASE 
            WHEN OpeningBalance > 0 THEN OpeningBalance 
            ELSE 0 
          END AS Debit, 
          CASE 
            WHEN OpeningBalance < 0 THEN OpeningBalance * - 1 
            ELSE 0 
          END AS Credit
        FROM ChartofAccounts
        WHERE (AccountCode = @AccountCode)
    ) AS OpeningData
    RETURN @Balance
END

但是，如果我在查询分析器中运行此查询，它会给我所需的答案。