巧用sql事半功倍

在mybatis里,曾经踩过几次坑,也用了一些mysql的技巧来应用数据库的功能减少编码的复杂性,尤其是批量操作,下面配合mybatis的应用总结一下4个小技巧(1 传0值 2 批量insert 3 批量update 4 批量insert or update) 。先创建一张表order_item(订单表)如下:

CREATE TABLE `order_item` (
   `id` bigint(20)  unsigned NOT NULL AUTO_INCREMENT COMMENT'自增主键',
    `order_date` date NOT NULL  COMMENT  '订单日期(2017-10-10)',
    `order_type`  tinyint(4) NOT NULL  COMMENT  '订单类型',
    `user_id`  varchar(30) NOT NULL DEFAULT  ''  COMMENT  '用户ID',
    `order_no`  varchar(30) NOT NULL DEFAULT  ''  COMMENT  '订单编码',
    `is_deleted`  tinyint(4) NOT NULL DEFAULT  0 COMMENT  '删除标志(0 未删除 1 删除)',
    PRIMARY KEY(`id`),
    UNIQUE KEY `uniq_orderNo` (`order_no`)
)ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COMMENT '订单表';

1 mybatis传值0,很多时候回忽略 0==isDeleted 导致0传值失败

 
     and is_deleted = #{isDeleted}
 

2 insert批量写入

   
      INSERT INTO order_item (
      order_date,
      order_type,
      user_id,
      order_no,
      is_deleted)
      VALUES
    
           (#{item.orderDate},
           #{item.orderType},
           #{item.userId},
           #{item.orderNo},
          #{item.isDeleted} )
       
     ;
  

3 update批量更新,巧用"case ... then " 语句


    update order_item
    
    
    
         
             when id=#{i.id} then #{i.userId}
        
    
    
    
    where
    
      id=#{i.id}
   

4 设置unique key,insert 或 update只需一个方法,巧用" ON DUPLICATE KEY "


    INSERT INTO order_item (
    order_date,
    order_type,
    user_id,
    order_no,
    is_deleted)
    VALUES
  
    (#{item.orderDate},
    #{item.orderType},
    #{item.userId},
    #{item.orderNo},
    #{item.isDeleted} )
  
    ON DUPLICATE KEY
    UPDATE
    order_date=VALUES(orderDate),
    order_type=VALUES(orderType),
    user_id=VALUES(userId),
    order_no=VALUES(orderNo),
    is_deleted=VALUES(isDeleted)
   ;

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