在 SQL Server 动态数据透视中分配默认值

Question

下面是我的要求的透视查询。

DECLARE @cols NVARCHAR(MAX) = '';

;WITH log_date AS 
(
    SELECT 
        BatchStartDate AS l_date 
    FROM 
        Table_Batch_Lookup

    UNION ALL

    SELECT 
        DATEADD(dd, 1, l_date) 
    FROM 
        log_date AS ld, Table_Batch_Lookup AS tb  
    WHERE 
        ld.l_date < DATEADD(dd, -1, tb.BatchEndDate)
)
SELECT 
    @cols = COALESCE (@cols + ',[' + CONVERT(NVARCHAR,CONVERT(VARCHAR(10), l_Date, 111), 106) + ']','[' + CONVERT(NVARCHAR, l_Date, 106) + ']') 
FROM 
    (SELECT DISTINCT CONVERT(VARCHAR(10), l_Date, 111) AS l_date 
     FROM log_date) PV;

DECLARE @totalScore INT = LEN(@cols) - LEN(REPLACE(@cols, ',', ''))

DECLARE @query NVARCHAR(MAX); 

SET @query = 'SELECT t_info.TraineeID,t_batch.BatchId,t_info.Name,t_info.Mobile'+@cols+'  FROM  Table_TraineeInfo AS t_info  Left JOIN       
                  (SELECT * FROM 
                 (
                     SELECT TraineeID,BatchId,Attendance,CONVERT(VARCHAR(10), l_Date, 111) AS l_date FROM Table_Attendance_Log
                 ) x
                 PIVOT 
                 (
                     MAX(Attendance)
                     FOR l_Date IN (' + right(@cols, len(@cols)-1)+ ')
                ) p ) AS f_pv ON t_info.TraineeID=f_pv.TraineeID JOIN Table_Batch_Lookup as t_batch ON t_batch.BatchId=t_info.BatchId

                WHERE t_batch.BatchId=45;
                ' ;    
    EXEC SP_EXECUTESQL @query;

下面是我的带有数据的表创建脚本的脚本。 Table_TraineeInfo是候选人注册明细表，Table_Batch_Lookup是批次开始日期和结束日期基于填写数据透视表时的批次明细， Table_Attendance_Log是考生考勤记录。

CREATE TABLE [dbo].[Table_TraineeInfo]
(
    [TraineeID] [INT] NULL,
    [BatchId] [INT] NULL,
    [Name] [VARCHAR](MAX) NULL,
    [Mobile] [VARCHAR](10) NULL
) ON [PRIMARY]
GO

SET ANSI_PADDING OFF
GO
INSERT [dbo].[Table_TraineeInfo] ([TraineeID], [BatchId], [Name], [Mobile]) 
VALUES (243, 45, N'demo201', N'9888562341'),
       (244, 45, N'demo202', N'9888562342'),
       (246, 45, N'demo204', N'9888562344'),
       (247, 45, N'demo205', N'9999999999')

/****** Object:  Table [dbo].[Table_Batch_Lookup]    Script Date: 12/15/2019 04:34:41 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO

CREATE TABLE [dbo].[Table_Batch_Lookup]
(
    [BatchId] [INT] NULL,
    [BatchStartDate] [DATETIME] NULL,
    [BatchEndDate] [DATETIME] NULL
) ON [PRIMARY]
GO

INSERT [dbo].[Table_Batch_Lookup] ([BatchId], [BatchStartDate], [BatchEndDate]) 
VALUES (45, CAST(0x0000AB2200000000 AS DateTime), CAST(0x0000AB25018B80D4 AS DateTime))

/****** Object:  Table [dbo].[Table_Attendance_Log]    Script Date: 12/15/2019 04:34:41 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
SET ANSI_PADDING ON
GO

CREATE TABLE [dbo].[Table_Attendance_Log]
(
    [TraineeID] [INT] NULL,
    [BatchId] [INT] NULL,
    [Attendance] [VARCHAR](10) NULL,
    [l_date] [DATETIME] NULL
) ON [PRIMARY]
GO

SET ANSI_PADDING OFF
GO

INSERT [dbo].[Table_Attendance_Log] ([TraineeID], [BatchId], [Attendance], [l_date]) 
VALUES (243, 45, N'Present', CAST(0x0000AB220127842A AS DateTime)),
       (243, 45, N'Present', CAST(0x0000AB2301281C2A AS DateTime)),
       (243, 45, N'Present', CAST(0x0000AB240128E416 AS DateTime)),
       (244, 45, N'Present', CAST(0x0000AB24012A05AB AS DateTime)),
       (246, 45, N'Present', CAST(0x0000AB23012B245A AS DateTime)),
       (246, 45, N'Present', CAST(0x0000AB24012B245A AS DateTime))

我当前的输出

如果日期小于或等于今天的日期，我希望下面的输出将空值填充到缺席（过去的日期），而未来的日期应该是 2019 年 12 月 16 日没有缺席的未来日期不需要填写缺席。

Answer 1

在常规（即非动态）透视查询中，当聚合函数产生null 时，您通常使用COALESCE() 来分配默认值。

这对于您的动态 SQL 来说有点复杂。基本上，您需要设置第二个变量来保存要放入 SELECT 子句中的 COALESCE() 表达式。我叫它@select_cols；我们使用COALESCE() 和CASE 表达式在分配默认值之前检查日期是否为未来。

这是您的更新代码：

Declare @cols NVARCHAR(Max)='';
Declare @select_cols NVARCHAR(Max)='';

;With log_date AS (
    SELECT BatchStartDate as l_date FROM Table_Batch_Lookup
    UNION ALL
    SELECT DATEADD(dd, 1, l_date)
    FROM log_date AS ld, Table_Batch_Lookup AS tb 
    WHERE ld.l_date < DATEADD(dd, -1, tb.BatchEndDate)
)
SELECT 
    @cols = COALESCE (
        @cols + ',[' + CONVERT(NVARCHAR,CONVERT(VARCHAR(10), l_Date, 111), 106) + ']',
        '[' + CONVERT(NVARCHAR, l_Date, 106) + ']'
    ), 
    @select_cols = COALESCE (
        @select_cols 
            + ',COALESCE([' + CONVERT(NVARCHAR,CONVERT(VARCHAR(10), l_Date, 111), 106) 
            + '], ' + CASE WHEN CONVERT(DATE, l_Date, 111) <= GETDATE() 
                THEN '''Absent''' 
                ELSE '''NULL''' 
            END + ') AS [' 
            + CONVERT(NVARCHAR,CONVERT(VARCHAR(10), l_Date, 111), 106) + ']',
        '[' + CONVERT(NVARCHAR, l_Date, 106) + ']'
    )
FROM (SELECT DISTINCT CONVERT(VARCHAR(10), l_Date, 111) AS l_date FROM log_date) PV

Declare @totalScore INT =len(@cols) - len(replace(@cols, ',', ''))

DECLARE @query NVARCHAR(MAX); 
SET @query = 'SELECT 
        t_info.TraineeID,
        t_batch.BatchId,
        t_info.Name,
        t_info.Mobile'
        + @select_cols + '
    FROM  Table_TraineeInfo AS t_info  
    LEFT JOIN (
            SELECT * FROM (
                 SELECT 
                     TraineeID,
                     BatchId,
                     Attendance,
                     CONVERT(VARCHAR(10), l_Date, 111) AS l_date 
                 FROM Table_Attendance_Log
            ) x
            PIVOT (
                 MAX(Attendance)
                 FOR l_Date IN (' + right(@cols, len(@cols)-1)+ ')
            ) p 
    ) AS f_pv ON t_info.TraineeID=f_pv.TraineeID 
    JOIN Table_Batch_Lookup as t_batch ON t_batch.BatchId=t_info.BatchId
    WHERE t_batch.BatchId=45';  

EXEC SP_EXECUTESQL @query;

Demo on DB Fiddle：

实习生ID |批号 |姓名 |手机 | 2019/12/13 | 2019/12/14 | 2019/12/15 | 2019/12/16 --------: | ------: | :-------- | :--------- | :--------- | :--------- | :--------- | :--------- 243 | 45 |演示201 | 9888562341 |礼物 |礼物 |礼物 |空值 244 | 45 |演示202 | 9888562342 |缺席 |缺席 |礼物 |空值 246 | 45 |演示204 | 9888562344 |缺席 |礼物 |礼物 |空值 247 | 45 |演示205 | 9999999999 |缺席 |缺席 |缺席 |空值