mysql 对已有数据的表换主键及主键初始化赋值

顺序执行以下sql语句
1.删除表主键约束

ALTER TABLE ba_shop DROP PRIMARY KEY;

2.添加新主键字段id

ALTER TABLE ba_shop ADD id BIGINT(20) NOT NULL COMMENT ‘主键’ FIRST;

3.id赋值

#显示行号的sql
SELECT
@r := @r + 1 AS row_num,a.*
FROM ba_shop a, (SELECT @r := 0) b;

4.把已经存在的行号当作主键赋值给主键

UPDATE ba_shop bs1
INNER JOIN (
	SELECT
		@r := @r + 1 AS row_num,
		bs2.shop_id
	FROM
		ba_shop bs2,
		(SELECT @r := 0) b
) tb ON bs1.shop_id = tb.shop_id
SET bs1.id = tb.row_num;

5.设置主键

ALTER TABLE ba_shop
  ADD PRIMARY KEY (`id`);