从表名中选择喜欢

Question

我在 SQL Server 数据库 (SSMS) 中有 1000 个表，并希望将 1000 个表中的选定列放入 1 个新表中。

我想做这样的事情

1. 创建一个包含 a、b、c 列的新表

2. 确定要从中选择数据的 1000 个表 - 要根据通配符之类的内容选择表名。

   在数据库中，有很多很多表，并且名称遵循类似的模式，例如ABC_0001, ABC_0002 ... ABC_1000, XYZ_0001, XYZ_0002, ... XYZ_1000 等...我只想选择以ABC 开头的表格..

3. 从这 1000 个表中选择列 a、b、c，并将值插入在步骤 #1 中创建的表中

我是这样做的：

SELECT a, b, c FROM ABC_0001 UNION_ALL
SELECT a, b, c FROM ABC_0002 UNION_ALL
SELECT a, b, c FROM ABC_1000 
INSERT INTO NEW_TABLE

并且想做类似的事情

SELECT a, b, c FROM TABLE LIKE ABC_% 
INSERT INTO NEW_TABLE

Answer 1

您可以使用Dynamic SQL 和CURSOR OR WHILE LOOP 来实现这一点，我使用CURSOR 实现了它。如果您不想在新表中插入重复条目，请使用 UNION 而不是 UNION ALL。

DROP TABLE IF EXISTS TABLE_NEW
CREATE TABLE TABLE_NEW (A VARCHAR,B VARCHAR, C VARCHAR) -- Modify according to your need
DECLARE @Sql NVARCHAR(MAX) = ''
,@TableName VARCHAR(500)
,@Id INT

DECLARE Table_Cursor CURSOR FOR 
SELECT 
ROW_NUMBER() OVER (ORDER BY TABLE_NAME ASC) Id
,TABLE_NAME 
FROM INFORMATION_SCHEMA.TABLES 
WHERE TABLE_TYPE = 'BASE TABLE' 
AND TABLE_NAME LIKE 'ABC_%'

OPEN Table_Cursor  
FETCH NEXT FROM Table_Cursor INTO @Id,@TableName 

WHILE @@FETCH_STATUS = 0  
BEGIN  
     IF(@Id = 1)
        BEGIN
            
            SET @Sql = @Sql + 'SELECT A, B, C FROM '+@TableName ----Modify the columns based on your column names
            SELECT @SQL
        END
     ELSE
        BEGIN
            SET @Sql = @Sql + ' UNION ALL SELECT A, B, C FROM '+@TableName --Modify the columns based on your column names
        END

     FETCH NEXT FROM Table_Cursor INTO @Id,@TableName
END 

CLOSE Table_Cursor  
DEALLOCATE Table_Cursor

INSERT INTO NEW_TABLE 
EXEC (@Sql)

根据您的新要求添加了以下答案。您可以检查table 中是否存在column，然后根据您得到的结果做出决定。我已经使用IIF() 和COL_LENGTH() 函数来实现这一点。

DROP TABLE IF EXISTS TABLE_NEW
CREATE TABLE TABLE_NEW (A VARCHAR,B VARCHAR, C VARCHAR) -- Modify according to your need
DECLARE @Sql NVARCHAR(MAX) = ''
,@TableName VARCHAR(500)
,@Id INT

DECLARE Table_Cursor CURSOR FOR 
SELECT 
ROW_NUMBER() OVER (ORDER BY TABLE_NAME ASC) Id
,TABLE_NAME 
FROM INFORMATION_SCHEMA.TABLES 
WHERE TABLE_TYPE = 'BASE TABLE' 
AND TABLE_NAME LIKE 'Temp%'

OPEN Table_Cursor  
FETCH NEXT FROM Table_Cursor INTO @Id,@TableName 

WHILE @@FETCH_STATUS = 0  
BEGIN  
     
     --Declare variables for all your columns here and assign the column name as the value

     DECLARE @A VARCHAR(100) = 'A', @B VARCHAR(100) = 'B',@C VARCHAR(100) = 'C'

     SELECT @A = IIF(COL_LENGTH(@TableName, @A)>0,@A,'NULL')
     SELECT @B = IIF(COL_LENGTH(@TableName, @B)>0,@B,'NULL')
     SELECT @C = IIF(COL_LENGTH(@TableName, @C)>0,@C,'NULL')

     IF(@Id = 1)
        BEGIN
            
            SET @Sql = @Sql + 'SELECT '+@A+' AS A, '+@B+' AS B, '+@C+' AS C FROM '+@TableName ----Modify the columns based on your column names
            SELECT @A AS A
        END
     ELSE
        BEGIN
            SET @Sql = @Sql + ' UNION ALL SELECT '+@A+' AS A, '+@B+' AS B, '+@C+' AS C FROM '+@TableName --Modify the columns based on your column names
        END

     FETCH NEXT FROM Table_Cursor INTO @Id,@TableName
END
CLOSE Table_Cursor  
DEALLOCATE Table_Cursor

INSERT INTO TABLE_NEW
SELECT @SQL

Answer 2

您可以执行以下操作：

-- use 'UNION' to select only distinct values, and UNION ALL if you want to select all rows

SELECT * 
    INTO [NEW_TABLE]
        FROM ABC_001
            UNION ALL
        SELECT * FROM ABC_002
            UNION ALL
        SELECT * FROM ABC_003
            UNION ALL
        -- and so on...
        SELECT * FROM ABC_999
        -- there's no need to use UNION on the last select

如果您真的不想键入所有 999 多个表，您可以编写一个存储过程以从名称与您所需模式匹配的表中进行选择。

参考资料：
https://www.w3schools.com/sql/sql_ref_union.asp
SELECT INTO USING UNION QUERY
SQL Server select data from 100+ tables