如何从动态表名中进行选择

Question

我有这样的桌子

changes201101
changes201102
changes201103
...
changes201201

还有桌子 whichchanges 其中包含行 Year 和 MONTH

如何从 whichchanges 的更改中选择 *？

我输入这个查询

SET @b := SELECT CONCAT('changes',year,month) FROM whichchanges;
((((@b should contain now multiple rows of changesYearMonth)))))
SET @x := SELECT * FROM @b;
Prepare stmt FROM @b;
Prepare stmt FROM @x;
Execute stmt;

#1064 - 您的 SQL 语法有错误；检查与您的 MySQL 服务器版本相对应的手册，以在第 1 行的 'SELECT CONCAT('changes',year,month) FROM changes)' 附近使用正确的语法

Answer 1

您打开 1 个 ( 并关闭 2 个 )。删除最后一个：

SELECT CONCAT('changes',year,month) FROM changes

编辑

第二个语句应该是

SET @x := SELECT * FROM (@b) as b;

这可行，但不确定这是否是您想要的：

SET @b := 'SELECT CONCAT(''changes'',`year`,`month`) FROM whichchanges';
SET @x := 'SELECT * FROM (SELECT CONCAT(''changes'',`year`,`month`) FROM whichchanges) as b';
Prepare stmt FROM @b;
Prepare stmt FROM @x;
Execute stmt;

编辑2

如果我理解正确，您正在寻找单个查询：

select * from changes
where change_column in (select distinct concat(`year`, `month`) from whichchanges)

编辑3

select @b := group_concat(concat(' select * from changes', `year`, `month`, ' union ') separator ' ') as w from whichchanges;
set @b := left(@b, length(@b) - 6);

Prepare stmt FROM @b;
Execute stmt;

SQLFiddle example