sql - 从具有动态表名的各种表中进行 SQL 查询

Question

我的数据库包含自 2009 年以来每个月的日志。每个表名都遵循以下模式： dbo.LOG[year][month] --> dbo.LOG200909 现在我需要合并所有这些表来运行查询。是否有任何捷径可以做到这一点，而无需通过硬编码表名将它们一一合并，例如将来需要较少维护的名称范围？因为这些表一直在添加，我希望查询继续使用新添加的表。顺便说一句，我对 SQL 几乎是新手。

Answer 1

您可以使用存储过程：

DROP Procedure IF EXISTS test_procedure;
GO

CREATE PROCEDURE test_procedure
    (@prefix Nvarchar(100),
    @start_year int,
    @start_month int,
    @end_year int,
    @end_month int
    )
AS
BEGIN
    declare @sql varchar(8000)
    declare @year int
    set @year = @start_year + 1
    select @sql='select * from  ' + @prefix + CAST(@start_year as varchar(10))
    WHILE @year <= @end_year
    BEGIN
        select @sql +=' union ' + @prefix + CAST(@year as varchar(10))
        SET @year = @year + 1
    END
    select @sql
    --execute(@sql)
END;
GO

exec test_procedure @prefix = 'abc', @start_year = 2000, @start_month=1, @end_year = 2005, @end_month=1;

这将导致：“select * from abc2000 union abc2001 union abc2002 union abc2003 union abc2004 union abc2005”

您可以使用“执行”来运行它，而不是打印该语句。

您需要增强循环来计算月份。

Answer 2

DECLARE myCursor cursor 
    FOR SELECT QUOTENAME(T.TABLE_SCHEMA)+'.'+QUOTENAME(T.TABLE_NAME) TABLE_NAME
          FROM INFORMATION_SCHEMA.TABLES T
         WHERE T.TABLE_NAME LIKE 'Log20[0-9][0-9][0-1][0-9]' 
           AND T.TABLE_SCHEMA = 'dbo'
         ORDER BY T.TABLE_NAME;
    
    IF OBJECT_ID('tempdb..#Results','U') IS NOT NULL
        DROP TABLE #Results;
    
    CREATE TABLE #Results -- Same structure as Log tables
    (
        Col1 int,
        Col2 nvarchar(20)
        -- ,...
    );
    
    OPEN myCursor
    
    DECLARE @TABLE_NAME sysname
    FETCH NEXT FROM myCursor INTO @TABLE_NAME 
    WHILE @@FETCH_STATUS = 0 BEGIN
        DECLARE @sSql as nvarchar(MAX)
        SET @sSql = 'INSERT INTO #Results(col1,Col2, Col2...) '
                  + 'SELECT * FROM ' + @TABLE_NAME
        EXEC(@sSql);
    
        FETCH NEXT FROM myCursor INTO @TABLE_NAME 
    END
    CLOSE myCursor
    DEALLOCATE myCursor
    
    
    SELECT *
     FROM #Results