Question

我有一个sql查询，如果在查询执行后没有结果集，我想将值返回为“NULL”。我已经尝试过ISNULL属性，但是它产生了错误，

我的查询是：

SELECT ISNULL((SELECT TOP (100) PERCENT a.ReportDate, a.Scripcode, a.ISIN, a.Scripname, a.AccountNo, a.ClientLongName, a.GroupName, a.Event, a.TradedQty, a.UnreconQty, a.ExDateQty, a.RecDateQty, a.Diff, a.Rate, a.Ratio, a.TotalValue, a.Shares, a.StartDate, a.ExDate, a.RecordDate, a.PayDate, a.AgmDate, a.NSecName, a.NSecNo, a.Remark, b.GRUL_PROX_GRP_ID, b.GRUL_GROUPNO, b.CUSTOMERNO, b.GRUL_SHORTNAME, b.GRUP_SHORTCODE, b.CONF_TYP, b.SWIFT, b.FAX, b.COURIER, b.EMAIL, b.Account_Group, b.Excel_Word, b.Password, b.Sub_Account_Flag 
FROM       dbo.CRS_Entitlement_MasterDate AS a 
INNER JOIN dbo.CRS_Entitlement_EntitlementComn AS b 
ON         a.AccountNo = b.CUSTOMERNO
WHERE      (b.Account_Group = 'A') 
AND        (b.Excel_Word = 'E') 
AND        (b.SWIFT <> 'v') 
AND        (b.CONF_TYP <> 'N/A') 
AND        (b.FAX = 'v') 
OR         (b.Account_Group = 'A') 
AND        (b.Excel_Word = 'E') 
AND        (b.SWIFT <> 'v') 
AND        (b.CONF_TYP <> 'N/A') 
AND        (b.COURIER = 'v') 
OR         (b.Account_Group = 'A') 
AND        (b.Excel_Word = 'E') 
AND        (b.SWIFT <> 'v') 
AND        (b.CONF_TYP <> 'N/A') 
AND        (b.EMAIL = 'v')
ORDER BY   a.AccountNo), 0) AS Expr1

请帮我解决这个问题，在此先感谢!!!

Answer 1

像这样使用EXISTS：

-- returns NULL when it doesn't exist
SELECT  CASE WHEN EXISTS ( SELECT   1 AS val
                           WHERE    1 = 2 ) THEN 1
             ELSE NULL
        END RESULT;

-- returns something else, in this case 1 when it does exist    
SELECT  CASE WHEN EXISTS ( SELECT   1 AS val
                           WHERE    1 = 1 ) THEN 1
             ELSE NULL
        END RESULT;

EXISTS（Transact-SQL）

指定要测试行是否存在的子查询。

包含数据的示例：

CREATE TABLE #test ( id INT );

INSERT  INTO #test
        ( id )
VALUES  ( 1 ),
        ( 2 ),
        ( 3 );

-- returns data
IF ( EXISTS ( SELECT    *
              FROM      #test
              WHERE     id > 0 ) )
    SELECT  *
    FROM    #test
    WHERE   id > 0;
ELSE
    SELECT  NULL;

 -- returns NULL 
 IF ( EXISTS ( SELECT    *
              FROM      #test
              WHERE     id > 5 ) )
    SELECT  *
    FROM    #test
    WHERE   id > 5;
ELSE
    SELECT  NULL AS Result;


DROP TABLE #test;

Answer 2

你不能在内部查询中放置多个列。对于ex select（100）％a.ReportDate ----将起作用

如果SQL查询在SQL中返回零值，如何将结果返回为NULL

2 个答案: