Question

我正在从一个系统迁移到另一个系统，在此过程中，我将同时运行两个系统。我需要能够在保持每个表的主键的同时，从一个表到另一个表单向同步。

在这个例子中，我有两个表（A）和（B）。我需要根据公共外键（下面的match1和match2）将表B中的value1和value2（下面）同步到表A.表A将包含除表B之外的其他字段，并且B中的某些字段将不会同步。

如何执行以下操作：

将已添加到B
从A中删除已从B
使用B

以下是一些演示数据：

DROP TABLE IF EXISTS `a`;
CREATE TABLE IF NOT EXISTS `a` (
  `id1` int(10) unsigned NOT NULL,
  `match1` int(10) unsigned NOT NULL,
  `value1` varchar(255) NOT NULL,
  PRIMARY KEY  (`id1`)
);

INSERT INTO `a` (`id1`, `match1`, `value1`) VALUES
(1, 1, 'A'),
(2, 2, 'A'),
(3, 3, 'B'),
(4, 4, 'C'),
(5, 5, 'C');

DROP TABLE IF EXISTS `b`;
CREATE TABLE IF NOT EXISTS `b` (
  `id2` int(10) unsigned NOT NULL,
  `match2` int(10) unsigned NOT NULL,
  `value2` varchar(255) NOT NULL,
  PRIMARY KEY  (`id2`)
);

INSERT INTO `b` (`id2`, `match2`, `value2`) VALUES
(1, 1, 'A'),
(2, 2, 'A'),
(3, 3, 'B'),
(4, 5, 'D'),
(5, 6, 'D'),
(6, 7, 'F');

我目前的方向是在两个表之间创建一个合并表，并相应地构建查询。例如：

create table ab as (select * from a, b);

你有什么建议？

Answer 1

1.插入已添加到B

的所有内容

INSERT INTO a(id1, match1, value1)
SELECT id2, match2, value2
FROM b WHERE NOT EXISTS (SELECT 1 FROM a WHERE a.match1 = b.match2)

2.从A中删除所有已从B

删除的内容

DELETE FROM a
WHERE match1 IN (SELECT match1 FROM a INNER JOIN B ON A.match1 = B.match2)

3.使用B

中更改的字段更新A.

UPDATE a
SET value1 = (SELECT value2 FROM b WHERE a.match1 = b.match2)

Answer 2

我构建了一个存储过程来正确合并所有内容。谢谢你的回复。这就是我要去的地方。

BEGIN

DECLARE loop_done INT;
DECLARE orphan varchar(255);
DECLARE CONTINUE HANDLER FOR NOT FOUND SET loop_done=1;

INSERT INTO a(id1, match1, value1)
SELECT '', match2, value2
FROM b WHERE NOT EXISTS (SELECT 1 FROM a WHERE a.match1 = b.match2);

UPDATE a SET value1 = (SELECT value2 FROM b WHERE a.match1 = b.match2);

/* This Delete statement works better for MySQL. */
SET loop_done=0;
SET orphan=null;
SELECT id1 INTO orphan FROM a left join b on (b.match2 = a.match1) where b.id2 is null LIMIT 1;
WHILE (loop_done=0) DO
 DELETE FROM a WHERE id1=orphan;
 SELECT id1 INTO orphan FROM a left join b on (b.match2 = a.match1) where b.id2 is null LIMIT 1;
END WHILE;

END

Answer 3

TRUNCATE TABLE A;

INSERT INTO A (id1, match1, value1)
    SELECT id2, match2, value2 FROM B;

如何同步两个具有不同结构的MySQL表？

3 个答案: