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jookr
V2EX  ›  MySQL

捣鼓一下午到现在还没解决的一句简单 SQL 语句求赐教:两张表关联查询求总数降序排列

  •  
  •   jookr · 2015-12-08 21:25:25 +08:00 · 2521 次点击
    这是一个创建于 3255 天前的主题,其中的信息可能已经有所发展或是发生改变。
    表 member


    表 city



    查表 [ member as m ] 的数据总量 [ count(*) as total ]
    顺带一起展示 city 表的 [ c.id,c.city_name,c.pinyin ]
    关联另外一张表 [ left join city as c ]
    关系是 member 的 m.from 关联 city 的 c.pinyin [ on m.from=c.pinyin ]
    按照 c.pinyin 分组 [ group by c.pinyin ]
    按照 total 降序排列 [ order by total desc ]


    自己测试过以下语句
    select c.id,c.city_name,c.pinyin,count(*) as total
    from `city` as c
    left join `member` as m on m.from = c.pinyin
    group by c.pinyin
    order by total desc
    空记录的深圳本该是 0 ,但是查出来竟然是 1 。


    select c.id,c.city_name,c.pinyin,count(*) as total
    from `city` as c
    left join `member` as m on m.from = c.pinyin
    group by c.id
    order by total desc
    空记录的深圳本该是 0 ,但是查出来竟然是 1 。

    select c.id,c.city_name,c.pinyin,count(*) as total
    from `city` as c
    left join `member` as m on m.from = c.pinyin
    group by c.city_name
    order by total desc
    空记录的深圳本该是 0 ,但是查出来竟然是 1 。

    以上三条 sql 结果一样,如下图

    =================================


    select c.id,c.city_name,c.pinyin,count(*) as total
    from `member` as m
    left join `city` as c on m.from = c.pinyin
    group by m.from
    order by total desc
    少了 0 数据的深圳,数据不全。

    select c.id,c.city_name,c.pinyin,count(*) as total
    from `member` as m
    left join `city` as c on m.from = c.pinyin
    group by c.city_name
    order by total desc
    少了 0 数据的深圳,数据不全。

    select c.id,c.city_name,c.pinyin,count(*) as total
    from `member` as m
    left join `city` as c on m.from = c.pinyin
    group by c.pinyin
    order by total desc
    少了 0 数据的深圳,数据不全。

    以上三条 sql 结果一样,如下图


    =====================================
    --
    -- 表的结构 `city`
    --

    CREATE TABLE IF NOT EXISTS `city` (
    `id` int(11) NOT NULL AUTO_INCREMENT,
    `city_name` varchar(30) NOT NULL,
    `pinyin` varchar(30) NOT NULL,
    PRIMARY KEY (`id`)
    ) ENGINE=MyISAM DEFAULT CHARSET=utf8 AUTO_INCREMENT=6 ;


    INSERT INTO `city` (`id`, `city_name`, `pinyin`) VALUES
    (1, '北京', 'beijing'),
    (2, '上海', 'shanghai'),
    (3, '广州', 'guangzhou'),
    (4, '深圳', 'shenzhen'),
    (5, '未知', '');
    ================================

    --
    -- 表的结构 `member`
    --

    CREATE TABLE IF NOT EXISTS `member` (
    `id` int(11) NOT NULL AUTO_INCREMENT,
    `name` varchar(30) NOT NULL,
    `from` varchar(30) NOT NULL,
    PRIMARY KEY (`id`)
    ) ENGINE=MyISAM DEFAULT CHARSET=utf8 AUTO_INCREMENT=10 ;



    INSERT INTO `member` (`id`, `name`, `from`) VALUES
    (1, 'a1', 'beijing'),
    (2, 'a2', 'beijing'),
    (3, 'a3', 'beijing'),
    (4, 'a4', 'shanghai'),
    (5, 'a5', 'shanghai'),
    (6, 'a6', 'guangzhou'),
    (7, 'a7', ''),
    (8, 'a8', ''),
    (9, 'a9', '');
    ==================================
    请问如何写这条 sql 语句才能正确的查询如第一段想要的结果呢?
    5 条回复    2015-12-24 12:19:33 +08:00
    terence4444
        1
    terence4444  
       2015-12-08 21:34:40 +08:00   ❤️ 1
    粗看了一下,你把 city 表放左边似乎是不对的,应该挂右表。
    cxbig
        2
    cxbig  
       2015-12-08 21:38:37 +08:00   ❤️ 1
    跟 city 相关的信息都放 city 表,和 member 的关联只给一个 city_id 。
    统计的时候 city 做主表,连上 member , count 一下就好。
    alex321
        3
    alex321  
       2015-12-08 21:41:19 +08:00   ❤️ 1
    SELECT `member`.*,`city`.*,count(`member`.id) AS total
    FROM member
    RIGHT JOIN city ON `member`.`from`=`city`.`pinyin`
    GROUP BY `city`.`id`
    ORDER BY total DESC

    你要统计的是按照城市来,请使用 right join 。。
    jookr
        4
    jookr  
    OP
       2015-12-08 21:47:56 +08:00
    原来如此 谢谢各位
    看来得重温 mysql 基础知识了
    soolby
        5
    soolby  
       2015-12-24 12:19:33 +08:00
    过来问问楼主你还健身吗?
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