douai2499
douai2499
采纳率100%
2014-09-01 10:06

Mysql在复杂查询中使用GROUP_CONCAT加入

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我遇到了一个运行查询的问题,我有三个表:

categories

| id  | name       | 
| --- | ---------- | 
| 1   | Logo       | 
| 2   | Poster     |
| 3   | Stationary | 
| 4   | Web        |
| 5   | Projects   | 
| 6   | Sporadic   | 

photos

| id  | portid | image            | preveiw |
| --- | ------ | ---------------- | ------- |
| 171 | 30     | a30preview.jpg   | 1       |
| 172 | 30     | b30.jpg          |         |
| 173 | 30     | c30.jpg          |         |
| 174 | 32     | a32preview.jpg   | 1       |
| 175 | 32     | b32.jpg          |         |
| 176 | 33     | a33preview.jpg   | 1       |
| 179 | 33     | b33.jpg          |         |
| 180 | 41     | a41preview.jpg   | 1       |

portfolios

| id  | catid  | type  | title        | text         | date   |
| --- | ------ | ----- | ------------ | ------------ | ------ |
| 30  | 2      | M     | xxxxxxxx     | xxxxxxxx     | xxxxxx |
| 32  | 2      | M     | xxxxxx       | xxxxxx       | xxxxxx |
| 33  | 2      | L     | xxxxxxxxxx   | xxxxxxxxxx   | xxxxxx |
| 41  | 1      | L     | xxxx         | xxxx         | xxxxxx |
| 45  | 2      | L     | xxxxx        | xxxxx        | xxxxxx | <-(This record has no image in 'photos' table, so it's not in 'output')

我想把这些记录作为输出(其中name=‘post’):

| id  | catid  | name     | type  | title        | text         | date   | image   <-(first image is the one that has 'photos.preview' = 1)|
| --- | ------ | -------- | ----- | ------------ | ------------ | ------ | ---------------------------------- |
| 30  | 2      | Poster   | M     | xxxxxxxx     | xxxxxxxx     | xxxxxx | a30preview.jpg, b30.jpg, c30.jpg   |
| 32  | 2      | Poster   | M     | xxxxxx       | xxxxxx       | xxxxxx | a32preview.jpg, b32.jpg            |
| 33  | 2      | Poster   | L     | xxxxxxxxxx   | xxxxxxxxxx   | xxxxxx | a33preview.jpg, b33.jpg            |

我尝试过以下SQL语句:

select * from `portfolios` 
   inner join `categories` on `portfolios`.`catid` = `categories`.`id` 
   inner join `photos` on `portid` = `portfolios`.`id` 
where `categories`.`name` = "Poster"

当然,它不起作用,因为我不知道我应该把GROUP_CONCAT放在哪里。

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3条回答

  • douyanyan1123 douyanyan1123 7年前

    Considering, that GROUP_CONCAT() is an aggregate function, you have to use GROUP BY to get desired resultset. You may try this:

    SELECT
        `portfolios`.*,
        `categories`.*,
        GROUP_CONCAT(
            `photos`.`image`
                ORDER BY `photos`.`preveiw` DESC
                SEPARATOR ', '
        ) as `image`
    FROM
       `portfolios` 
           INNER JOIN `categories` ON `portfolios`.`catid` = `categories`.`id` 
           INNER JOIN `photos` ON `portid` = `portfolios`.`id` 
    WHERE
        `categories`.`name` = 'Poster'
    GROUP BY
        `portfolios`.`id`
    
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  • dongzhong7443 dongzhong7443 7年前

    It will be a lot easier if you spell out the columns instead of using *:

    select p.id, p.catid, c.name, p.type, p.title
         , p.text, p.date. group_concat(ph.image order by case when ph.previw = 1 
                                                               then 0 else 1 
                                                          end) as images 
    from `portfolios` p 
    join `categories` c
        on p.`catid` = c.`id` 
    join `photos` ph
        on ph.`portid` = p.`id` 
    where c.`name` = "Poster"
    group by p.id, p.catid, c.name, p.type, p.title
           , p.text, p.date 
    
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  • duanhu7390 duanhu7390 7年前
    SELECT portfolios.*, categories.*, GROUP_CONCAT(photos.image) AS image
    FROM `portfolios` 
    inner join `categories` on `portfolios`.`catid` = `categories`.`id` 
    inner join `photos` on `portid` = `portfolios`.`id` 
    where `categories`.`name` = "Poster"
    GROUP BY portfolios.id
    
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