Question

我有一个问题，我认为其中一个问题会在底部解决，但我仍然有问题。问题是我的案例陈述是错误的（但运行没有错误）但不确定我还缺少什么。

我的目标是，如果DueDate为NULL，因为Table2中没有记录，因此我想要的是将此值显示为＆＃39; No＆＃39;而不是＆＃39; NULL＆＃39;。我添加了＃34; IsNull＆＃34;进入我的代码，但还没有解决我的问题。我在这些论坛上看过ISNULL（）和COALEASE（），但无法得到我想要的结果

以下是我的工作代码：

SELECT 
    Client, 
    COUNT(*) AS ReadyRecords, 
    (SELECT COUNT(*) FROM Table1 EPR WHERE actioned=8 AND EPR.Client=Table1.Client) AS Outstanding, 
    (SELECT TOP 1 
        CASE 
            WHEN DueDate < GETDATE() THEN 'Yes' 
            WHEN DueDate IS NULL THEN 'No' 
        ELSE 'No' 
        END AS DueDate
    FROM Table2 GL WHERE GL.Client=Table1.Client ORDER BY DueDate) AS DueDate

    FROM Table1 WHERE Actioned=2 GROUP BY Client

编辑：

当前结果集：

Client   | ReadyRecords  |  Outstanding  |  DueDate

Test     |     42        |      54       |   NULL
Stack    |     150       |      10       |   NULL
JBloggs  |     32        |      28       |   Yes
DBloggs  |     2         |      17       |   Yes
Overflow |     1         |      1        |   No

期望的结果集：

Client   | ReadyRecords  |  Outstanding  |  DueDate

Test     |     42        |      54       |   No
Stack    |     150       |      10       |   No
JBloggs  |     32        |      28       |   Yes
DBloggs  |     2         |      17       |   Yes
Overflow |     1         |      1        |   No

表1：

id      |  Client   |   Actioned  | etc...

5245    |  Test     |      8      | etc...
....so on

表2：

id   |   Client   |   DueDate

1    |  JBloggs   | 2012-12-01 00:00:00.000
2    |  DBloggs   | 2012-12-05 00:00:00.000
3    |  Overflow  | 2012-12-12 00:00:00.000

如果您还有其他需要，请告诉我。

相似/相关问题：

Answer 1

您需要将ISNULL()或COALESCE()函数应用于整个内联子查询，如下所示：

SELECT 
    Client, 
    COUNT(*) AS ReadyRecords, 
    (SELECT COUNT(*) FROM Table1 EPR 
     WHERE actioned=8 AND EPR.Client=Table1.Client
    ) AS Outstanding, 

    COALESCE(
        (SELECT TOP 1 
            CASE 
                WHEN DueDate < GETDATE() THEN 'Yes' 
            END AS DueDate
        FROM Table2 GL WHERE GL.Client=Table1.Client ORDER BY DueDate
        ), 'No' 
    ) AS DueDate

FROM Table1  WHERE Actioned=2  GROUP BY Client ;

或将CASE表达式移到那里：

SELECT 
    Client, 
    COUNT(*) AS ReadyRecords, 
    (SELECT COUNT(*) FROM Table1 EPR 
     WHERE actioned=8 AND EPR.Client=Table1.Client
    ) AS Outstanding, 

    CASE WHEN 
           (SELECT TOP 1 
              DueDate
            FROM Table2 GL WHERE GL.Client=Table1.Client ORDER BY DueDate
           ) < GETDATE() 
        THEN 'Yes'
        ELSE 'No'
    END AS DueDate

FROM Table1  WHERE Actioned=2  GROUP BY Client ;

Answer 2

首先，您需要知道，表中的datetime字段可能显示为NULL，但在查询中使用它时，sql会将其转换为该数据类型允许的最小日期，即'1900-01 -01'所以你可能得到比实际值更多的'是'。

Answer 3

You can use this...
SELECT 
Client, 
COUNT(*) AS ReadyRecords, 
(SELECT COUNT(*) FROM Table1 EPR WHERE actioned=8 AND EPR.Client=Table1.Client) AS Outstanding, 
(SELECT TOP 1 
    CASE 
        WHEN DueDate < GETDATE() THEN 'Yes' 
        ELSE ISNULL(Cast(DueDate AS VARCHAR),'NO' )        
    END AS DueDate
FROM Table2 GL WHERE GL.Client=Table1.Client ORDER BY DueDate) AS DueDate

FROM Table1 WHERE Actioned=2 GROUP BY Client

Answer 4

我认为问题是如果DueDate为NULL，则DueDate < GetDate()结果为NULL，结果为No，因为DueDate在这种情况下永远不会低于GetDate。像这样更改订单

CASE 
    WHEN DueDate IS NULL THEN 'No'
    WHEN DueDate < GETDATE() THEN 'Yes'        
ELSE 'No' 
END AS DueDate

通过这样做，在其他条件之前首先检查NULL值。或者，您可以将此行更改为

WHEN ISNULL(DueDate,'Some Valid Default Value Here') < GETDATE() THEN 'Yes'

Answer 5

这是否有效 - 怀疑其中可能存在一些故障，但我目前没有管理层：

SELECT 
        Client, 
        COUNT(*) AS ReadyRecords, 
        (SELECT COUNT(*) FROM Table1 EPR WHERE actioned=8 AND EPR.Client=Table1.Client) AS Outstanding, 
        [DueDate] = CASE 
                                WHEN [MXDATE] < GETDATE() THEN 'Yes' 
                                WHEN [MXDATE] IS NULL THEN 'No' 
                            ELSE 'No' 
                            END 
FROM 
    Table1 T1
    LEFT OUTER JOIN
        (
        SELECT 
            Client,
            [MXDATE] = MAX(DueDate)
        FROM Table2
            GROUP BY Client
        ) GL
        ON
         GL.Client=T1.Client 
WHERE Actioned=2 
GROUP BY Client

SQL - CASE语句如果记录为NULL，因为表中不存在记录

5 个答案: