#头条创作挑战赛#

涉及循环、动态sql等主要的MySQL存储过程知识。

需求：

遍历所有【test_ondev_[0-9]】开头的表，将其中的所有数据按表中的col字段存储到【test_ondev_history_ + col的值】的表里面，当【test_ondev_history_ + col】不存在的时候复制test_ondev_history的结构创建该表，并将数据存储进表里。

程序思路:

遍历表名将每张表的col字段的内容统计出来创建 test_ondev_history_ + col 的表将数据插入进去test_ondev_history_ + col表中继续遍历其他表

使用存储过程实现：

DELIMITER $$CREATE PROCEDURE `p_copy_data`()    BEGIN        DECLARE i INT;       DECLARE  v_sql_col VARCHAR(200);    DECLARE j INT;    DECLARE max_id_s INT;    DECLARE max_id INT;    DECLARE v_tbname VARCHAR(50);    DECLARE v_tbname_s VARCHAR(50);    DECLARE v_col VARCHAR(50);    DECLARE  v_sql_create VARCHAR(200);    DECLARE  v_sql_insert VARCHAR(200);        CREATE TABLE IF NOT EXISTS temp_col(id INT PRIMARY KEY AUTO_INCREMENT,col VARCHAR(50));    CREATE TABLE IF NOT EXISTS tbnames(id INT PRIMARY KEY AUTO_INCREMENT,tbname VARCHAR(50));    TRUNCATE TABLE tbnames;    INSERT INTO tbnames(tbname)    SELECT  table_name FROM information_schema.`TABLES` WHERE table_name REGEXP   'test_ondev_[0-9]';      SET i = (SELECT MIN(id) FROM   tbnames);     SET  max_id_s = (SELECT MAX(id) FROM   tbnames);            WHILE  i <=max_id_s    DO    TRUNCATE TABLE  temp_col;    SET v_tbname_s = (SELECT tbname FROM  tbnames  WHERE id = i);    SET v_sql_col = CONCAT('insert into temp_col(col)  select distinct   col  from  ',v_tbname_s);      SET  @v_sql_col := v_sql_col;    PREPARE stmt FROM @v_sql_col;        EXECUTE stmt ;      DEALLOCATE PREPARE stmt;     SET j =1;    SET  max_id = (SELECT  MAX(id) FROM temp_col );    WHILE  j <= max_id    DO    SET  v_col = (SELECT col  FROM temp_col  WHERE id =j);    SET v_tbname = CONCAT('test_ondev_history_',v_col );    SET v_sql_create = CONCAT('create table  if not exists ',v_tbname,'  like test_ondev_history;');      SET  @v_sql_create := v_sql_create;    PREPARE stmt FROM @v_sql_create;        EXECUTE stmt ;      DEALLOCATE PREPARE stmt;         SET  v_sql_insert = CONCAT('insert into ',v_tbname,' select * from ',v_tbname_s," where  col='", v_col ,"';");                SET  @v_sql_insert := v_sql_insert;    PREPARE stmt FROM @v_sql_insert;        EXECUTE stmt ;      DEALLOCATE PREPARE stmt;         SET j = j + 1;    END WHILE;        SET  i = i + 1;    END  WHILE;        END$$

TIPS：

MySQL不建议使用存储过程，如果临时用的话可以考虑临时使用。

另外，该过程是第一版实现历史数据的迁移，如果需要重复执行还有不少优化空间，例如：

遍历表的时候需要指定对应库；上述过程不能重复执行，如果重复执行，需要怎么改进；中途涉及创建表，如果不创建哪些临时表改如何调整；

这些就留给大家思考了，也欢迎来和我沟通。文章如果有误，欢迎斧正 ，非常感谢。