MySQL存儲過程舉例

涉及循環、動態sql等主要的MySQL存儲過程知識。

需求:

遍歷所有【test_ondev_[0-9]】開頭的表,將其中的所有數據按表中的col字段存儲到【test_ondev_history_ + col的值】的表裏面,當【test_ondev_history_ + col】不存在的時候複製test_ondev_history的結構創建該表,並將數據存儲進表裡。
程序思路:

  • 遍歷表名
  • 將每張表的col字段的內容統計出來
  • 創建 test_ondev_history_ + col 的表
  • 將數據插入進去test_ondev_history_ + col表中
  • 繼續遍歷其他表

使用存儲過程實現:

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不建議使用存儲過程,如果臨時用的話可以考慮臨時使用。

另外,該過程是第一版實現歷史數據的遷移,如果需要重複執行還有不少優化空間,例如:

  • 遍歷表的時候需要指定對應庫;
  • 上述過程不能重複執行,如果重複執行,需要怎麼改進;
  • 中途涉及創建表,如果不創建哪些臨時表改如何調整;

這些就留給大家思考了,也歡迎來和我溝通。文章如果有誤,歡迎斧正 ,非常感謝。