MySQL存储过程举例

gjc592 2020-05-07 原文

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_ + disCode的值】的表里面，当【test_ondev_history_ + disCode】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。

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$$