• 中文
    • English
  • 注册
  • 查看作者
  • 5-14:多表删除

    一.  多表删除的语法结构

    DELETE tbl_name[.*][,tbl_name[.*]]...
    FROM table_references
    [WHERE where_condition]

    首先查看一下tdb_goods表中的所有记录:

    mysql> SELECT goods_id,goods_name FROM tdb_goods;
    +----------+---------------------------------------------------------------------
    | goods_id | goods_name                                                         
    +----------+--------------------------------------------------------------------
    |        1 | R510VC 15.6英寸笔记本                                                
    |        2 | Y400N 14.0英寸笔记本电脑                                                    
    |        3 | G150TH 15.6英寸游戏本                                                 
    |        4 | X550CC 15.6英寸笔记本                                                    
    |        5 | X240(20ALA0EYCD) 12.5英寸超极本                                            
    |        6 | U330P 13.3英寸超极本                                                     
    |        7 | SVP13226SCB 13.3英寸触控超极本                                                 
    |        8 | iPad mini MD531CH/A 7.9英寸平板电脑                                             
    |        9 | iPad Air MD788CH/A 9.7英寸平板电脑 (16G WiFi版)                                 
    |       10 |  iPad mini ME279CH/A 配备 Retina 显示屏 7.9英寸平板电脑 (16G WiFi版)                     
    |       11 | IdeaCentre C340 20英寸一体电脑                                                   
    |       12 | Vostro 3800-R1206 台式电脑                                                   
    |       13 | iMac ME086CH/A 21.5英寸一体电脑                                                 
    |       14 | AT7-7414LP 台式电脑 (i5-3450四核 4G 500G 2G独显 DVD 键鼠 Linux )                 
    |       15 | Z220SFF F4F06PA工作站                                                      
    |       16 | PowerEdge T110 II服务器                                                   
    |       17 | Mac Pro MD878CH/A 专业级台式电脑                                            
    |       18 |  HMZ-T3W 头戴显示设备                                                 
    |       19 | 商务双肩背包                                                        
    |       20 | X3250 M4机架式服务器 2583i14                                        
    |       21 |  HMZ-T3W 头戴显示设备                                               
    |       22 | 商务双肩背包                                                       
    |       23 |  LaserJet Pro P1606dn 黑白激光打印机                                
    +----------+-----------------------------------------------------------------------
    23 rows in set (0.00 sec)

    可以看到18和21还有19和22这几条记录是完全相同的,首先找出所有的重复记录:

    mysql> SELECT goods_id,goods_name FROM tdb_goods GROUP BY goods_name HAVING count(goods_name) >= 2;
    +----------+-----------------------+
    | goods_id | goods_name            |
    +----------+-----------------------+
    |       18 |  HMZ-T3W 头戴显示设备         |
    |       19 | 商务双肩背包                   |
    +----------+-----------------------+
    2 rows in set (0.00 sec)

    删除和18、19重复的记录:

    (感谢此处@ytcfighting的指正)

    DELETE t1 FROM tdb_goods AS t1 LEFT JOIN
    (SELECT goods_id, goods_name FROM tdb_goods 
    GROUP BY goods_name HAVING count(goods_name)>=2)
    AS t2 ON t1.goods_name=t2.goods_name WHERE t1.goods_id >t2.goods_id;

    再次查看记录可以看到已经删除成功

    mysql> SELECT * FROM tdb_goods\G
    *************************** 1. row ***************************
       goods_id: 1
     goods_name: R510VC 15.6英寸笔记本
        cate_id: 5
       brand_id: 2
    goods_price: 3399.000
        is_show: 1
     is_saleoff: 0
    *************************** 2. row ***************************
       goods_id: 2
     goods_name: Y400N 14.0英寸笔记本电脑
        cate_id: 5
       brand_id: 7
    goods_price: 4899.000
        is_show: 1
     is_saleoff: 0
    *************************** 3. row ***************************
       goods_id: 3
     goods_name: G150TH 15.6英寸游戏本
        cate_id: 4
       brand_id: 9
    goods_price: 8499.000
        is_show: 1
     is_saleoff: 0
    *************************** 4. row ***************************
       goods_id: 4
     goods_name: X550CC 15.6英寸笔记本
        cate_id: 5
       brand_id: 2
    goods_price: 2799.000
        is_show: 1
     is_saleoff: 0
    *************************** 5. row ***************************
       goods_id: 5
     goods_name: X240(20ALA0EYCD) 12.5英寸超极本
        cate_id: 7
       brand_id: 7
    goods_price: 4999.000
        is_show: 1
     is_saleoff: 0
    *************************** 6. row ***************************
       goods_id: 6
     goods_name: U330P 13.3英寸超极本
        cate_id: 7
       brand_id: 7
    goods_price: 4299.000
        is_show: 1
     is_saleoff: 0
    *************************** 7. row ***************************
       goods_id: 7
     goods_name: SVP13226SCB 13.3英寸触控超极本
        cate_id: 7
       brand_id: 6
    goods_price: 7999.000
        is_show: 1
     is_saleoff: 0
    *************************** 8. row ***************************
       goods_id: 8
     goods_name: iPad mini MD531CH/A 7.9英寸平板电脑
        cate_id: 2
       brand_id: 8
    goods_price: 1998.000
        is_show: 1
     is_saleoff: 0
    *************************** 9. row ***************************
       goods_id: 9
     goods_name: iPad Air MD788CH/A 9.7英寸平板电脑 (16G WiFi版)
        cate_id: 2
       brand_id: 8
    goods_price: 3388.000
        is_show: 1
     is_saleoff: 0
    *************************** 10. row ***************************
       goods_id: 10
     goods_name:  iPad mini ME279CH/A 配备 Retina 显示屏 7.9英寸平板电脑 (16G WiFi版)
        cate_id: 2
       brand_id: 8
    goods_price: 2788.000
        is_show: 1
     is_saleoff: 0
    *************************** 11. row ***************************
       goods_id: 11
     goods_name: IdeaCentre C340 20英寸一体电脑
        cate_id: 1
       brand_id: 7
    goods_price: 3499.000
        is_show: 1
     is_saleoff: 0
    *************************** 12. row ***************************
       goods_id: 12
     goods_name: Vostro 3800-R1206 台式电脑
        cate_id: 1
       brand_id: 5
    goods_price: 2899.000
        is_show: 1
     is_saleoff: 0
    *************************** 13. row ***************************
       goods_id: 13
     goods_name: iMac ME086CH/A 21.5英寸一体电脑
        cate_id: 1
       brand_id: 8
    goods_price: 9188.000
        is_show: 1
     is_saleoff: 0
    *************************** 14. row ***************************
       goods_id: 14
     goods_name: AT7-7414LP 台式电脑 (i5-3450四核 4G 500G 2G独显 DVD 键鼠 Linux )
        cate_id: 1
       brand_id: 3
    goods_price: 3699.000
        is_show: 1
     is_saleoff: 0
    *************************** 15. row ***************************
       goods_id: 15
     goods_name: Z220SFF F4F06PA工作站
        cate_id: 3
       brand_id: 4
    goods_price: 4288.000
        is_show: 1
     is_saleoff: 0
    *************************** 16. row ***************************
       goods_id: 16
     goods_name: PowerEdge T110 II服务器
        cate_id: 3
       brand_id: 5
    goods_price: 5388.000
        is_show: 1
     is_saleoff: 0
    *************************** 17. row ***************************
       goods_id: 17
     goods_name: Mac Pro MD878CH/A 专业级台式电脑
        cate_id: 3
       brand_id: 8
    goods_price: 28888.000
        is_show: 1
     is_saleoff: 0
    *************************** 18. row ***************************
       goods_id: 18
     goods_name:  HMZ-T3W 头戴显示设备
        cate_id: 6
       brand_id: 6
    goods_price: 6999.000
        is_show: 1
     is_saleoff: 0
    *************************** 19. row ***************************
       goods_id: 19
     goods_name: 商务双肩背包
        cate_id: 6
       brand_id: 6
    goods_price: 99.000
        is_show: 1
     is_saleoff: 0
    *************************** 20. row ***************************
       goods_id: 20
     goods_name: X3250 M4机架式服务器 2583i14
        cate_id: 3
       brand_id: 1
    goods_price: 6888.000
        is_show: 1
     is_saleoff: 0
    *************************** 21. row ***************************
       goods_id: 23
     goods_name:  LaserJet Pro P1606dn 黑白激光打印机
        cate_id: 12
       brand_id: 4
    goods_price: 1849.000
        is_show: 1
     is_saleoff: 0
    21 rows in set (0.00 sec)

  • 0
  • 2
  • 0
  • 3.1k
  • 请登录之后再进行评论

    登录
  • 0
    张甲49站长
    @ytcfighting 十分感谢,已经更正!
  • 0
    DELETE t1FROM tdb_goods AS t1 LEFT JOIN(SELECT goods_id, goods_name FROM tdb_goods GROUP BY goods_name HAVING count(goods_name)>=2)AS t2 ON t1.goods_name=t2.goods_name WHERE t1.goods_id >t2.goods_id;
    忘写删除语句了
  • 单栏布局 侧栏位置: