MYSQL 如何联合多个 "Unknown" 表

Question

我有一些结构为 "TableNameYYMM" 的历史表如何 UNION 所有以 "TableName" 开头的历史表？

我需要搜索所有历史表。

我用 PREPARE Execute 和 DEALLOCATE 试过了。但我每次都会收到 SQL 错误。

SET group_concat_max_len = 2048;

SET @startQuery = (SELECT CONCAT('SELECT col1, col2, col3 FROM ',TABLE_SCHEMA,'.', TABLE_NAME)
FROM information_schema.tables 
WHERE 
    ENGINE = 'MyISAM'
    AND TABLE_NAME like 'hist%'
ORDER BY TABLE_NAME
LIMIT 0,1);



SET @subquery = (SELECT GROUP_CONCAT(@startquery, 'UNION ALL SELECT col1, col2, col3 FROM ',TABLE_SCHEMA,'.', TABLE_NAME)
FROM information_schema.tables 
WHERE 
    ENGINE = 'MyISAM'
    AND TABLE_NAME like 'hist%'
ORDER BY TABLE_NAME
LIMIT 1,1000);


PREPARE stmt1 FROM '? AS combinedTable';
EXECUTE stmt1 USING @subquery;
DEALLOCATE PREPARE stmt1;

在第 1 部分 (@startquery) 我尝试获取查询的第一部分 "select xxx from table1"

在第 2 部分 (@subquery) 我试图获取所有联合（来自 table2-max 1000）

select xxx from table1
UNION ALL select xxx from table2
UNION ALL select xxx from table3
...

我希望有人对这个问题有想法。

Answer 1

/*
create table history1701 (id int,col1 int,col2 int);
create table history1702 (id int,col1 int,col2 int);
create table history1703 (id int,col1 int,col2 int);
create table history1704 (id int,col1 int,col2 int);
insert into history1701 values (1,1,1);
insert into history1702 values (2,2,2);
insert into history1703 values (3,3,3);
insert into history1704 values (4,4,4);
*/

SET @startQuery = (SELECT CONCAT('SELECT col1, col2 FROM ',TABLE_SCHEMA,'.', TABLE_NAME)
FROM information_schema.tables 
WHERE 
#    ENGINE = 'MyISAM'    AND 
    TABLE_NAME like 'hist%17%'
ORDER BY TABLE_NAME
LIMIT 0,1);

SET @subquery = (
SELECT group_CONCAT(' UNION ALL SELECT col1, col2 FROM ',TABLE_SCHEMA,'.', TABLE_NAME order by table_name separator ' ' )
FROM information_schema.tables 
WHERE 
     TABLE_NAME like 'hist%17%'
     and table_name <> (
     select table_name from information_schema.tables WHERE 
#    ENGINE = 'MyISAM'    AND 
    TABLE_NAME like 'hist%17%'
    ORDER BY TABLE_NAME
    LIMIT 0,1
    )
);


select @startquery;
set @subquery = concat(@startquery,@subquery);

PREPARE stmt1 FROM @subquery;
EXECUTE stmt1 ;

DEALLOCATE PREPARE stmt1;

在你的代码中，第一个限制 1,1000 @subquery returns 一个空值（不好）并在每个 union all 之后生成一个逗号（也不好）。我对此进行了修改以排除第一个历史记录 table 并将组连接分隔符更改为 space 并将顺序移动到 group_concat.

内

MYSQL 如何联合多个 "Unknown" 表

MYSQL How to UNION Multiple "Unknown" Tables

mysql

union

prepare