Sql 如何连接到名称作为值存储在另一个表中的表？_Sql_Sql Server_Sql Server 2012_Dynamic Sql_Cursors

Sql 如何连接到名称作为值存储在另一个表中的表？

sql sql-server sql-server-2012

Sql 如何连接到名称作为值存储在另一个表中的表？,sql,sql-server,sql-server-2012,dynamic-sql,cursors,Sql,Sql Server,Sql Server 2012,Dynamic Sql,Cursors,我有一些表（例如，[Table1]，[Table2]，[Table3]等等），每个表上都有一个[ID]主键和一个RecTime日期时间 ΑlsoⅧ有一个表[Files]，该表将文件保存在varbinary（max）列中，并引用具有名称和ID的其他表 [Table2]、[Table3]以及其他一些具有不同结构的文件，但它们共享的[ID]和[RecTime]列与[Table1]中的列完全相同下面是一个可视化数据的快速示例 DECLARE @Table1 as table ( [ID]

我有一些表（例如，

[Table1]

，

[Table2]

，

[Table3]

等等），每个表上都有一个

[ID]

主键和一个

RecTime

日期时间

ΑlsoⅧ有一个表

[Files]

，该表将文件保存在

varbinary（max）

列中，并引用具有名称和ID的其他表

[Table2]

、

[Table3]

以及其他一些具有不同结构的文件，但它们共享的

[ID]

和

[RecTime]

列与

[Table1]

中的列完全相同

下面是一个可视化数据的快速示例

DECLARE @Table1 as table (
      [ID] [bigint]
    , [RecTime] [datetime]
)
DECLARE @Table2 as table (
      [ID] [bigint]
    , [RecTime] [datetime]
)
DECLARE @Table3 as table (
      [ID] [bigint]
    , [RecTime] [datetime]
)

DECLARE @Files as table (
      [ID] [bigint]
    , [tblName] nvarchar(255) NULL
    , [tblID] bigint NULL
    , [BinaryData]  varbinary(max)
    /* and some other columns */
)

INSERT INTO @Table1 (
      [ID]
    , [RecTime]
)
          SELECT '1', DATEADD(day, (ABS(CHECKSUM(NEWID())) % 65530), 0)
UNION ALL SELECT '2', DATEADD(day, (ABS(CHECKSUM(NEWID())) % 65530), 0)
UNION ALL SELECT '3', DATEADD(day, (ABS(CHECKSUM(NEWID())) % 65530), 0)
UNION ALL SELECT '4', DATEADD(day, (ABS(CHECKSUM(NEWID())) % 65530), 0)
UNION ALL SELECT '5', DATEADD(day, (ABS(CHECKSUM(NEWID())) % 65530), 0)

INSERT INTO @Table2 (
      [ID]
    , [RecTime]
)
          SELECT '11', DATEADD(day, (ABS(CHECKSUM(NEWID())) % 65530), 0)
UNION ALL SELECT '12', DATEADD(day, (ABS(CHECKSUM(NEWID())) % 65530), 0)
UNION ALL SELECT '13', DATEADD(day, (ABS(CHECKSUM(NEWID())) % 65530), 0)
UNION ALL SELECT '14', DATEADD(day, (ABS(CHECKSUM(NEWID())) % 65530), 0)
UNION ALL SELECT '15', DATEADD(day, (ABS(CHECKSUM(NEWID())) % 65530), 0)

INSERT INTO @Table3 (
      [ID]
    , [RecTime]
)
          SELECT '21', DATEADD(day, (ABS(CHECKSUM(NEWID())) % 65530), 0)
UNION ALL SELECT '22', DATEADD(day, (ABS(CHECKSUM(NEWID())) % 65530), 0)
UNION ALL SELECT '23', DATEADD(day, (ABS(CHECKSUM(NEWID())) % 65530), 0)
UNION ALL SELECT '24', DATEADD(day, (ABS(CHECKSUM(NEWID())) % 65530), 0)
UNION ALL SELECT '25', DATEADD(day, (ABS(CHECKSUM(NEWID())) % 65530), 0)

INSERT INTO @Files (
      [ID]
    , [tblName]
    , [tblID]
    , [BinaryData]
)
          SELECT '1', 'Table1', '1', 0x010203040506
UNION ALL SELECT '2', 'Table1', '2', 0x010203040506
UNION ALL SELECT '3', 'Table1', '2', 0x010203040506
UNION ALL SELECT '4', 'Table1', '3', 0x010203040506
UNION ALL SELECT '5', 'Table1', '4', 0x010203040506
UNION ALL SELECT '6', 'Table1', '5', 0x010203040506
UNION ALL SELECT '7', 'Table1', '5', 0x010203040506

UNION ALL SELECT '8', 'Table2', '11', 0x010203040506
UNION ALL SELECT '9', 'Table2', '11', 0x010203040506
UNION ALL SELECT '10', 'Table2', '12', 0x010203040506
UNION ALL SELECT '11', 'Table2', '13', 0x010203040506
UNION ALL SELECT '12', 'Table2', '14', 0x010203040506
UNION ALL SELECT '13', 'Table2', '12', 0x010203040506
UNION ALL SELECT '14', 'Table2', '15', 0x010203040506

UNION ALL SELECT '15', 'Table3', '21', 0x010203040506
UNION ALL SELECT '16', 'Table3', '22', 0x010203040506
UNION ALL SELECT '17', 'Table3', '24', 0x010203040506
UNION ALL SELECT '18', 'Table3', '23', 0x010203040506
UNION ALL SELECT '19', 'Table3', '25', 0x010203040506
UNION ALL SELECT '20', 'Table3', '25', 0x010203040506
UNION ALL SELECT '21', 'Table3', '21', 0x010203040506

SELECT * FROM @Table1
SELECT * FROM @Table2
SELECT * FROM @Table3

SELECT * FROM @Files

如何将

[Files]

表连接到其他表，这些表的

名称

和

ID

源自“[Files]”表中的值

我需要

[Files]

表中的

[BinaryData]

，以及

[Files]

表中相应的表引用中的

[RecTime]

真正的问题是

[Table1]

、

[Table2]

和

[Table3]

并不是唯一引用
[Files]
表的表。可以创建新表，二进制数据必须存储在
[文件]
表中
所以我在寻找一种动态“加入”他们的方法
另外，我不是这个系统的创造者，也不能对它进行任何结构上的改变，只是试图解决这个问题
任何帮助都将不胜感激。
请尝试以下方法

Select res.* , F.* From Files F Left join ( Select 'table1' as tablename, a.* From table1 a Union Select 'table2' as tablename, b.* From table2 b Union Select 'table3' as tablename, c.* From table3 c )Res On res.tablename = F.tblname
一种解决方案是使用为
@Files
表中的每一行执行一些的：

-- Copy table variables into temporary tables so they can be referenced from dynamic SQL SELECT * INTO #Table1 FROM @Table1; SELECT * INTO #Table2 FROM @Table2; SELECT * INTO #Table3 FROM @Table3; -- Create a temporary table for storing the results CREATE TABLE #results ( [ID] [bigint] , [tblName] nvarchar(255) NULL , [tblID] bigint NULL , [BinaryData] varbinary(max) , [RecTime] [datetime] ); -- Declare placeholders and cursor DECLARE @ID bigint; DECLARE @tblName nvarchar(255); DECLARE @tblID bigint; DECLARE @BinaryData varbinary(max); DECLARE @RecTime datetime; DECLARE @sql nvarchar(max); DECLARE @params nvarchar(max); DECLARE files_cursor CURSOR FOR SELECT ID, tblName, tblID, BinaryData FROM @Files -- Loop over all rows in the @Files table OPEN files_cursor FETCH NEXT FROM files_cursor INTO @ID, @tblName, @tblID, @BinaryData WHILE @@FETCH_STATUS = 0 BEGIN -- Find the referenced table row and extract its RecTime. SET @RecTime = NULL; SET @sql = CONCAT( 'SELECT @RecTime = RecTime FROM #', @tblName, ' WHERE ID = ', @tblID); SET @params = '@RecTime datetime out'; EXEC SP_EXECUTESQL @sql, @params, @RecTime out; -- Add result INSERT INTO #results (ID, tblName, tblID, BinaryData, RecTime) VALUES (@ID, @tblName, @tblID, @BinaryData, @RecTime); FETCH NEXT FROM files_cursor INTO @ID, @tblName, @tblID, @BinaryData; END -- Finalise CLOSE files_cursor; DEALLOCATE files_cursor; -- Display the results from temporary table SELECT * FROM #results;

在线演示：
这是执行上述操作的最简单方法。不需要循环或任何东西。您需要动态代码，因为可以随时添加表
注意：在
文件的示例数据中
表的
tblId
中似乎有错误的数据
因此，我正在更改您的数据，以便将ID与相应的表相匹配
模式：

CREATE TABLE Table1 ( [ID] [bigint] , [RecTime] [datetime] ) CREATE TABLE Table2 ( [ID] [bigint] , [RecTime] [datetime] ) CREATE TABLE Table3 ( [ID] [bigint] , [RecTime] [datetime] ) CREATE TABLE Files ( [ID] [bigint] , [tblName] nvarchar(255) NULL , [tblID] bigint NULL , [BinaryData] varbinary(max) /* and some other columns */ ) INSERT INTO Table1 ( [ID] , [RecTime] ) SELECT '1', DATEADD(day, (ABS(CHECKSUM(NEWID())) % 65530), 0) UNION ALL SELECT '2', DATEADD(day, (ABS(CHECKSUM(NEWID())) % 65530), 0) UNION ALL SELECT '3', DATEADD(day, (ABS(CHECKSUM(NEWID())) % 65530), 0) UNION ALL SELECT '4', DATEADD(day, (ABS(CHECKSUM(NEWID())) % 65530), 0) UNION ALL SELECT '5', DATEADD(day, (ABS(CHECKSUM(NEWID())) % 65530), 0) INSERT INTO Table2 ( [ID] , [RecTime] ) SELECT '11', DATEADD(day, (ABS(CHECKSUM(NEWID())) % 65530), 0) UNION ALL SELECT '12', DATEADD(day, (ABS(CHECKSUM(NEWID())) % 65530), 0) UNION ALL SELECT '13', DATEADD(day, (ABS(CHECKSUM(NEWID())) % 65530), 0) UNION ALL SELECT '14', DATEADD(day, (ABS(CHECKSUM(NEWID())) % 65530), 0) UNION ALL SELECT '15', DATEADD(day, (ABS(CHECKSUM(NEWID())) % 65530), 0) INSERT INTO Table3 ( [ID] , [RecTime] ) SELECT '21', DATEADD(day, (ABS(CHECKSUM(NEWID())) % 65530), 0) UNION ALL SELECT '22', DATEADD(day, (ABS(CHECKSUM(NEWID())) % 65530), 0) UNION ALL SELECT '23', DATEADD(day, (ABS(CHECKSUM(NEWID())) % 65530), 0) UNION ALL SELECT '24', DATEADD(day, (ABS(CHECKSUM(NEWID())) % 65530), 0) UNION ALL SELECT '25', DATEADD(day, (ABS(CHECKSUM(NEWID())) % 65530), 0) INSERT INTO Files ( [ID] , [tblName] , [tblID] , [BinaryData] ) SELECT '1', 'Table1', '1', 0x010203040506 UNION ALL SELECT '2', 'Table1', '2', 0x010203040506 UNION ALL SELECT '3', 'Table1', '2', 0x010203040506 UNION ALL SELECT '4', 'Table1', '3', 0x010203040506 UNION ALL SELECT '5', 'Table1', '4', 0x010203040506 UNION ALL SELECT '6', 'Table1', '5', 0x010203040506 UNION ALL SELECT '7', 'Table1', '5', 0x010203040506 UNION ALL SELECT '8', 'Table2', '11', 0x010203040506 UNION ALL SELECT '9', 'Table2', '11', 0x010203040506 UNION ALL SELECT '10', 'Table2', '12', 0x010203040506 UNION ALL SELECT '11', 'Table2', '13', 0x010203040506 UNION ALL SELECT '12', 'Table2', '14', 0x010203040506 UNION ALL SELECT '13', 'Table2', '12', 0x010203040506 UNION ALL SELECT '14', 'Table2', '15', 0x010203040506 UNION ALL SELECT '15', 'Table3', '21', 0x010203040506 UNION ALL SELECT '16', 'Table3', '22', 0x010203040506 UNION ALL SELECT '17', 'Table3', '24', 0x010203040506 UNION ALL SELECT '18', 'Table3', '23', 0x010203040506 UNION ALL SELECT '19', 'Table3', '25', 0x010203040506 UNION ALL SELECT '20', 'Table3', '25', 0x010203040506 UNION ALL SELECT '21', 'Table3', '21', 0x010203040506
现在您的动态查询部分：

CREATE TABLE Table1 ( [ID] [bigint] , [RecTime] [datetime] ) CREATE TABLE Table2 ( [ID] [bigint] , [RecTime] [datetime] ) CREATE TABLE Table3 ( [ID] [bigint] , [RecTime] [datetime] ) CREATE TABLE Files ( [ID] [bigint] , [tblName] nvarchar(255) NULL , [tblID] bigint NULL , [BinaryData] varbinary(max) /* and some other columns */ ) INSERT INTO Table1 ( [ID] , [RecTime] ) SELECT '1', DATEADD(day, (ABS(CHECKSUM(NEWID())) % 65530), 0) UNION ALL SELECT '2', DATEADD(day, (ABS(CHECKSUM(NEWID())) % 65530), 0) UNION ALL SELECT '3', DATEADD(day, (ABS(CHECKSUM(NEWID())) % 65530), 0) UNION ALL SELECT '4', DATEADD(day, (ABS(CHECKSUM(NEWID())) % 65530), 0) UNION ALL SELECT '5', DATEADD(day, (ABS(CHECKSUM(NEWID())) % 65530), 0) INSERT INTO Table2 ( [ID] , [RecTime] ) SELECT '11', DATEADD(day, (ABS(CHECKSUM(NEWID())) % 65530), 0) UNION ALL SELECT '12', DATEADD(day, (ABS(CHECKSUM(NEWID())) % 65530), 0) UNION ALL SELECT '13', DATEADD(day, (ABS(CHECKSUM(NEWID())) % 65530), 0) UNION ALL SELECT '14', DATEADD(day, (ABS(CHECKSUM(NEWID())) % 65530), 0) UNION ALL SELECT '15', DATEADD(day, (ABS(CHECKSUM(NEWID())) % 65530), 0) INSERT INTO Table3 ( [ID] , [RecTime] ) SELECT '21', DATEADD(day, (ABS(CHECKSUM(NEWID())) % 65530), 0) UNION ALL SELECT '22', DATEADD(day, (ABS(CHECKSUM(NEWID())) % 65530), 0) UNION ALL SELECT '23', DATEADD(day, (ABS(CHECKSUM(NEWID())) % 65530), 0) UNION ALL SELECT '24', DATEADD(day, (ABS(CHECKSUM(NEWID())) % 65530), 0) UNION ALL SELECT '25', DATEADD(day, (ABS(CHECKSUM(NEWID())) % 65530), 0) INSERT INTO Files ( [ID] , [tblName] , [tblID] , [BinaryData] ) SELECT '1', 'Table1', '1', 0x010203040506 UNION ALL SELECT '2', 'Table1', '2', 0x010203040506 UNION ALL SELECT '3', 'Table1', '2', 0x010203040506 UNION ALL SELECT '4', 'Table1', '3', 0x010203040506 UNION ALL SELECT '5', 'Table1', '4', 0x010203040506 UNION ALL SELECT '6', 'Table1', '5', 0x010203040506 UNION ALL SELECT '7', 'Table1', '5', 0x010203040506 UNION ALL SELECT '8', 'Table2', '11', 0x010203040506 UNION ALL SELECT '9', 'Table2', '11', 0x010203040506 UNION ALL SELECT '10', 'Table2', '12', 0x010203040506 UNION ALL SELECT '11', 'Table2', '13', 0x010203040506 UNION ALL SELECT '12', 'Table2', '14', 0x010203040506 UNION ALL SELECT '13', 'Table2', '12', 0x010203040506 UNION ALL SELECT '14', 'Table2', '15', 0x010203040506 UNION ALL SELECT '15', 'Table3', '21', 0x010203040506 UNION ALL SELECT '16', 'Table3', '22', 0x010203040506 UNION ALL SELECT '17', 'Table3', '24', 0x010203040506 UNION ALL SELECT '18', 'Table3', '23', 0x010203040506 UNION ALL SELECT '19', 'Table3', '25', 0x010203040506 UNION ALL SELECT '20', 'Table3', '25', 0x010203040506 UNION ALL SELECT '21', 'Table3', '21', 0x010203040506
如果您想查看
@Qry
包含的内容

/* Print Output: SELECT Files.ID,Files.BinaryData ,COALESCE(Table1.RecTime,Table2.RecTime,Table3.RecTime) AS RecTime FROM Files LEFT JOIN Table1 ON Files.tblID = Table1.ID AND Files.tblName= 'Table1' LEFT JOIN Table2 ON Files.tblID = Table2.ID AND Files.tblName= 'Table2' LEFT JOIN Table3 ON Files.tblID = Table3.ID AND Files.tblName= 'Table3' */

这种设计只是在ER中建模层次结构的一种方法。基本上，您有一个基于表名的物理分区表（即
Table1
，
Table2
等等）。因此，联接这些表的最简单方法是创建一个分区视图，然后联接它
在您的示例中，您只需执行以下操作：

CREATE VIEW vmAll AS SELECT 'Table1' AS 'tblName', [ID], [RecTime] FROM Table1 UNION ALL SELECT 'Table2' AS 'tblName', [ID], [RecTime] FROM Table2 UNION ALL SELECT 'Table3' AS 'tblName', [ID], [RecTime] FROM Table3; GO
现在只需像往常一样将其与
文件
表连接起来（记住也要指定分区字段）：
例如：

SELECT F.[ID] , F.[tblName] , F.[tblID] , F.[BinaryData] , A.RecTime FROM [Files] F LEFT OUTER JOIN vmAll A ON F.[ID] = A.[ID] AND F.tblName = A.tblName
给出了预期的结果：

请注意一件重要的事情：因为它是一个分区视图，所以SQL Server能够执行分区消除，从而大大加快连接速度（这里正确的术语应该是表消除）
例如，先前的执行计划是：

如果我们在分区列上添加筛选器谓词：

SELECT F.[ID] , F.[tblName] , F.[tblID] , F.[BinaryData] , A.RecTime FROM [Files] F LEFT OUTER JOIN vmAll A ON F.[ID] = A.[ID] AND F.tblName = A.tblName WHERE A.tblName = 'Table1'
我们将获得此执行计划（请注意，两个表根本没有扫描）：

当然，为了使用分区视图，您必须首先能够创建它。您可以通过以下查询以编程方式查找特定字段：

;WITH CTE AS ( SELECT C.object_id FROM sys.columns C INNER JOIN sys.objects O ON C.object_id = O.object_id WHERE (C.[name] = 'ID' OR C.[name] = 'RecTime') AND O.[type] = 'U' GROUP BY C.object_id HAVING COUNT(*) = 2 ) SELECT OBJECT_NAME(object_id), object_id FROM CTE;

一种方法是创建一个包含所有表数据的cte（当然，使用动态sql创建它），然后从左文件中选择并连接该cte
这样，动态sql的编写和维护非常简单，它生成的sql语句也非常简单：

DECLARE @SQL varchar(max) = '' SELECT @SQL = @SQL +' UNION ALL SELECT ID, RecTime, '''+ tblName +''' AS TableName FROM ' + tblName FROM ( SELECT DISTINCT tblName FROM files ) x -- replace the first 'UNION ALL' with ';WITH allTables as (' SELECT @SQL = STUFF(@SQL, 1, 11, ';WITH allTables as (') +') SELECT * FROM Files LEFT JOIN allTables ON(tblName = TableName AND tblId = allTables.Id)'
从中获得的sql statemet是：

;WITH allTables as ( SELECT ID, RecTime, 'Table1' AS TableName FROM Table1 UNION ALL SELECT ID, RecTime, 'Table2' AS TableName FROM Table2 UNION ALL SELECT ID, RecTime, 'Table3' AS TableName FROM Table3 ) SELECT * FROM Files LEFT JOIN allTables ON(tblName = TableName AND tblId = allTables.Id)
要执行它：

EXEC(@SQL)
结果:

ID tblName tblID BinaryData ID RecTime TableName 1 Table1 1 123456 1 31.03.2060 00:00:00 Table1 2 Table1 2 123456 2 03.12.1997 00:00:00 Table1 3 Table1 2 123456 2 03.12.1997 00:00:00 Table1 4 Table1 3 123456 3 02.07.2039 00:00:00 Table1 5 Table1 4 123456 4 17.06.1973 00:00:00 Table1 6 Table1 5 123456 5 06.12.2076 00:00:00 Table1 7 Table1 5 123456 5 06.12.2076 00:00:00 Table1 8 Table2 1 123456 NULL NULL NULL 9 Table2 3 123456 NULL NULL NULL 10 Table2 3 123456 NULL NULL NULL 11 Table2 4 123456 NULL NULL NULL 12 Table2 5 123456 NULL NULL NULL 13 Table2 5 123456 NULL NULL NULL 14 Table2 5 123456 NULL NULL NULL 15 Table3 1 123456 NULL NULL NULL 16 Table3 1 123456 NULL NULL NULL 17 Table3 1 123456 NULL NULL NULL 18 Table3 3 123456 NULL NULL NULL 19 Table3 3 123456 NULL NULL NULL 20 Table3 3 123456 NULL NULL NULL 21 Table3 4 123456 NULL NULL NULL

如果您只有很少的表，那么您可以这样做，它可以稍微快一点，因为它避免了动态SQL
如果你不知道会有多少张桌子或者桌子是否太多，那么看看其他的解决方案（我喜欢Steve chamber的解决方案）

SELECT F.*, RecTime = CASE tblName WHEN 'Table1' THEN COALESCE(T1.RecTime, NULL) WHEN 'Table2' THEN COALESCE(T2.RecTime, NULL) WHEN 'Table3' THEN COALESCE(T3.RecTime, NULL) ELSE NULL END FROM @Files F LEFT JOIN @Table1 T1 ON F.tblID = T1.ID LEFT JOIN @Table2 T2 ON F.tblID = T2.ID LEFT JOIN @Table3 T3 ON F.tblID = T3.ID

演示：
查看以下链接。这可能会解决你的问题
,，
正如我所提到的，[表1]、[表2]和[表3]并不是唯一的表格。可以创建新表，其二进制数据必须存储在[Files]表中。将此内联查询作为视图，然后在文件表中添加新表时更改视图。为此需求编写动态查询可能会影响性能。我发现这很有用。谢谢。请从文件中选择tblName、BinaryData、RecTime，f.tblID=t.id上的join table1 t，其中tblName='table1'联合所有选择tblName、BinaryData，从文件中选择RecTime，f.tblID=t.id上的join table2 t，其中tblName='table2'联合所有选择tblName、BinaryData，在f.tblID=t.id上的文件f join table3 t中的RecTime，其中tblName='table3'您需要在示例中用表名替换您是否尝试了动态查询并在最后执行了它？我认为您的问题是架构设计的问题之一。显然，实体之间存在一种未（正确）表示的关系。解决方案是否必须使用所述的模式/数据，或者使用替代数据库设计的解决方案是否达到了相同的目的？您的示例基于3个表，实际上可以有多少个表（即超过100个）？您好，请检查@Harun PrasadHi Steve回答的此链接，我有一个问题，为什么光标结果中的
Table2
和
Table3
的
RecTime
字段为
NULL
？例如，在
tblName
Table2
和
tblId
1
RecTime
中，字段值应该是
12.12.1934 00:00:00
我想是的，也许我没有看到表数据，表1的ID是1-5，表2的ID是11-15，表3的ID是21-25。但是文件表中的TBLID都是1-5，这就是为什么没有找到表2和表3。一些与性能相关的改进：-将临时表放在末尾-如果要使用游标，请使用fast\u f