sql - 在 SQL 中使用不带 ELSE 条件的 IF

Question

我只在@rowcount 大于0 时才尝试使用下面的查询来更新一些数据。但是，即使@RowCount 为0，它也会执行更新语句。有人可以帮忙看看这里有什么问题吗？如果@RowCount 为0，我什么都不想做。

我使用的是 SQL Server 2014。

    TRUNCATE TABLE Count1
    DECLARE @RowCount AS INT

    --insert data in a temporary table
    SELECT YEAR, S_ID
    into #Count1 FROM
    (SELECT DISTINCT D.YEAR, S_ID FROM SALES S JOIN TRANSACTIONS PT
    ON S.COMBINED_TXN_ID = PT.S_ID AND PT.TRANSACTION_TYPE = 'BILLING'
    JOIN DATE D ON D.DAY = S.DAY AND PT.DAY = S.DAY
    WHERE
    S.SALES_CUSTOMER    !=   PT.CUSTOMER)Counter1;

    --Store the rowcount in a temporary variable
    SET @RowCount = (SELECT Count(*) FROM #Count1) 

    --Fix the data with differences only if count>0
    IF @@ROWCOUNT > 0
    BEGIN
    UPDATE SALES
    SET SALES_CUSTOMER =  PT.CUSTOMER
    FROM SALES S
    JOIN TRANSACTIONS PT ON  S.COMBINED_TXN_ID = PT.S_ID
    JOIN DATE D ON D.DAY = S.DAY AND PT.DAY = S.DAY
    WHERE
    S_ID IN (SELECT S_ID FROM #Count1) 
    END;

Answer 1

@@ROWCOUNT返回受最后一条语句影响的行数。

用你自己的变量@RowCount 改变系统变量@@ROWCOUNT

--Store the rowcount in a temporary variable
SET @RowCount = (SELECT Count(*) FROM #Count1) 

--Fix the data with differences only if count>0
IF  @RowCount > 0