优化下面的sql语句，达到最优：DECLARE @dtNow VARCHAR(100) = CONVERT(VARCHAR(100),GETDATE(),23); SELECT TOP 1 k.Name kehuName ,ISNULL(MaskingApply.quanxianSum,0) quanxianSum FROM xykehu k WITH(NOLOCK) LEFT JOIN ( SELECT cs.quanxianSum,cs.AddTime FROM ClearShowApply cs WITH(NOLOCK) WHERE ISNULL(cs.IsDel,0)=0 AND cs.State='审批通过' AND cs.PowerEndTime > @dtNow AND cs.XyKehuId = @kehuId AND cs.UsersId= @userId UNION SELECT cs.quanxianSum,cs.AddTime FROM ClearShowApply cs WITH(NOLOCK) WHERE ISNULL(cs.IsDel,0)=0 AND cs.State='审批通过' AND cs.PowerEndTime > @dtNow AND cs.XyKehuId = @kehuId AND cs.CardId= @cardId ) MaskingApply ON 1 = 1 WHERE k.Id = @kehuId AND ISNULL(k.IsDel,0)=0 ORDER BY MaskingApply.AddTime DESC;

可以优化的地方如下：

1. 将GETDATE()函数调用提前到变量声明中，这样避免多次调用函数，提高效率。

2. 将SELECT TOP 1改为SELECT TOP(1)，这样可以提高SQL Server执行效率。

3. 将UNION改为UNION ALL，因为前一个查询结果集和后一个查询结果集不可能存在重复记录，所以使用UNION ALL可以提高效率。

4. 将LEFT JOIN改为INNER JOIN，因为WHERE子句中已经限定了ClearShowApply表中的条件，所以不需要使用LEFT JOIN。

优化后的SQL语句如下：

DECLARE @dtNow VARCHAR(100) = CONVERT(VARCHAR(100), GETDATE(), 23);

SELECT TOP (1)
    k.Name AS kehuName,
    ISNULL(MaskingApply.quanxianSum, 0) AS quanxianSum
FROM
    xykehu AS k WITH(NOLOCK)
    INNER JOIN (
        SELECT
            cs.quanxianSum,
            cs.AddTime
        FROM
            ClearShowApply AS cs WITH(NOLOCK)
        WHERE
            ISNULL(cs.IsDel, 0) = 0
            AND cs.State = '审批通过'
            AND cs.PowerEndTime > @dtNow
            AND cs.XyKehuId = @kehuId
            AND cs.UsersId = @userId

        UNION ALL

        SELECT
            cs.quanxianSum,
            cs.AddTime
        FROM
            ClearShowApply AS cs WITH(NOLOCK)
        WHERE
            ISNULL(cs.IsDel, 0) = 0
            AND cs.State = '审批通过'
            AND cs.PowerEndTime > @dtNow
            AND cs.XyKehuId = @kehuId
            AND cs.CardId = @cardId
    ) AS MaskingApply ON 1 = 1
WHERE
    k.Id = @kehuId
    AND ISNULL(k.IsDel, 0) = 0
ORDER BY
    MaskingApply.AddTime DESC;