Question

我的目标是将来自不同架构的表合并为一个单一的架构，因此我想执行此查询：

INSERT INTO inventory.maintenance
SELECT *
FROM (
    SELECT NULL, 'A' as department_id, maintenance.* FROM a_inventory.maintenance
    UNION
    SELECT NULL, 'B' as department_id, maintenance.* FROM b_inventory.maintenance
    UNION
    SELECT NULL, 'E' as department_id, maintenance.* FROM e_inventory.maintenance
    UNION
    SELECT NULL, 'L' as department_id, maintenance.* FROM l_inventory.maintenance
    UNION
    SELECT NULL, 'M' as department_id, maintenance.* FROM m_inventory.maintenance
) AS tmp_maintenance

我必须对许多不同的表执行此查询，并且并非所有部门中的所有表都如此。与其手动编写每个查询，不如增加一些自动化...

SET @department = ('A', 'B', 'E', 'L', 'M');
SET @connection = 'inventory';
SET @table = 'maintenance';

/* MAGIC HERE to create @union */

SET @s = CONCAT(
    'INSERT INTO ', @connection, '.', @table,
    'SELECT * FROM (', @union, ') AS tmp');

PREPARE stm1 FROM @s; EXECUTE stm1; DEALLOCATE PREPARE stm1;

我想从@union创建@department。我曾尝试使用REPEAT，但实际上并没有用。

Answer 1

解决此问题的一种可能方法。但是您需要在某个地方有一个表departments，并假设id是id时可以从中提取char：

SET @department = 'A,B,E,L,M' COLLATE utf8mb4_unicode_ci;
SET @connection = 'inventory';
SET @table = 'maintenance';

SET @union = '';
SELECT @union := CONCAT(
    @union, 
    ' SELECT NULL, "', id , '", ', 
    @table,'.* FROM ', id, '_', 
    @connection, '.', @table, 
    ' UNION '
)
FROM departments WHERE FIND_IN_SET(id, @department);

SELECT @union := SUBSTRING(@union, 1, LENGTH(@union) - LENGTH('UNION '));

SET @s = CONCAT(
    'INSERT INTO ', @connection, '.', @table, ' '
    '( SELECT * FROM (', @union, ') AS tmp)');

SELECT @s;

PREPARE stm1 FROM @s; EXECUTE stm1; DEALLOCATE PREPARE stm1;

如何从变量数组生成准备好的MySQL查询？

1 个答案: