sql-server-2008 - 尽管满足条件但 T-SQL IF block 不执行

Question

我正在处理以下 SQL 语句。我已将其缩减为说明问题所需的部分。

DECLARE @mwareId as int = 9647,
@startDate as datetime = '2011-07-20',
@endDate as datetime = '2011-07-20'

IF OBJECT_ID('tempdb..#tmpInvoiceList', 'U') IS NOT NULL DROP TABLE #tmpInvoiceList

-- Get base invoice list for customer
SELECT   invoiceId
        ,invoiceNumber
        ,customerId
        ,customerName
        ,customerCode
        ,createDate
        ,lastModifiedDate
        ,invoiceDate
        ,totalInvoiceAmount
        ,statusId
        ,isPaid
INTO #tmpInvoiceList
FROM    Invoice.Invoice

-- Apply date range if applicable
IF ( @startDate != NULL AND @endDate != NULL )
BEGIN
    DELETE FROM #tmpInvoiceList
    WHERE invoiceDate NOT BETWEEN @startDate AND @endDate
END

SELECT * FROM #tmpInvoiceList

我将@startDate 和@endDate 变量设置为日期值。问题是将日期范围应用于临时表的 if block 没有执行，尽管这两个变量都不为空，我找不到原因。

Answer 1

据我所知，TSQL 不支持 != 运算符进行空值检查。试试这个:

IF ( @startDate IS NOT NULL AND @endDate IS NOT NULL )