Laravel 5 - 检索数据库中每个类别的前 4 条记录答案

【问题标题】：Laravel 5 - Retrieve the first 4 records for each category in databaseLaravel 5 - 检索数据库中每个类别的前 4 条记录
【发布时间】：2016-01-31 17:36:30
【问题描述】：

我有一个图库图片的数据库表，按以下分类：

“公司”、“食物”、“公园”、“派对”、“游乐设施”、“学校”、“场地”

每张图片都分配有这些类别之一。

我正在构建一个主图库页面，我想在其中显示数据库中每个类别的最新 4 张图像。

有人可以帮助我如何构建查询吗？

查询开始如下：

Bugz\GalleryImage::

表结构

Schema::create('gallery_images', function (Blueprint $table) {

            //set the table engine:
            $table->engine = 'InnoDb';

            //define an auto-incrementing primary key:
            $table->increments('id');

            //define the general fields:
            $table->enum('gallery', array('corporate', 'food', 'park', 'parties', 'rides', 'schools', 'venue'))->default('corporate');
            $table->string('title');
            $table->string('content')->nullable()->default(null);

            //define the audit fields:
            $table->timestamps();
            $table->softDeletes();

        });

我还没有足够的 Eloquent 经验来编写更复杂的查询。

谢谢。

【问题讨论】：

请发表你的表结构和雄辩的名字。
@VishalPatel 这有帮助吗？

标签： php mysql laravel eloquent

【解决方案1】：

这是一种方法...

DROP TABLE IF EXISTS my_table;

CREATE TABLE my_table
(image_id INT NOT NULL ATO_INCREMENT PRIMARY KEY
, category ENUM('corporate', 'food', 'park', 'parties', 'rides', 'schools', 'venue') NOT NULL
);

INSERT INTO my_table (category) VALUES
('corporate'), 
('food'), 
('park'), 
('parties'), 
('rides'), 
('schools'), 
('venue'),
('rides'), 
('schools'), 
('venue'),
('food'), 
('park'), 
('parties'), 
('rides'), 
('corporate'), 
('food'), 
('park'), 
('food'), 
('park'), 
('parties'), 
('rides'), 
('food'), 
('park'), 
('food'), 
('corporate'), 
('rides'), 
('corporate'), 
('parties'), 
('rides'), 
('corporate'), 
('food'),
('schools'), 
('venue'),
('venue'),
('food'), 
('park'), 
('parties')
;

中间结果...

SELECT x.*
     , COUNT(y.image_id) temp_ranks_for_y
  FROM my_table x 
  JOIN my_table y   
    ON y.category = x.category 
   AND y.image_id >= x.image_id 
 GROUP 
    BY x.image_id;
+----------+-----------+-------------------+
| image_id | category  | temp_ranks_for_y  |
+----------+-----------+-------------------+
|        1 | corporate |                 5 |
|        2 | food      |                 8 |
|        3 | park      |                 6 |
|        4 | parties   |                 5 |
|        5 | rides     |                 6 |
|        6 | schools   |                 3 |
|        7 | venue     |                 4 |
|        8 | rides     |                 5 |
|        9 | schools   |                 2 |
|       10 | venue     |                 3 |
|       11 | food      |                 7 |
|       12 | park      |                 5 |
|       13 | parties   |                 4 |
|       14 | rides     |                 4 |
|       15 | corporate |                 4 |
|       16 | food      |                 6 |
|       17 | park      |                 4 |
|       18 | food      |                 5 |
|       19 | park      |                 3 |
|       20 | parties   |                 3 |
|       21 | rides     |                 3 |
|       22 | food      |                 4 |
|       23 | park      |                 2 |
|       24 | food      |                 3 |
|       25 | corporate |                 3 |
|       26 | rides     |                 2 |
|       27 | corporate |                 2 |
|       28 | parties   |                 2 |
|       29 | rides     |                 1 |
|       30 | corporate |                 1 |
|       31 | food      |                 2 |
|       32 | schools   |                 1 |
|       33 | venue     |                 2 |
|       34 | venue     |                 1 |
|       35 | food      |                 1 |
|       36 | park      |                 1 |
|       37 | parties   |                 1 |
+----------+-----------+-------------------+

所以...

SELECT x.* 
  FROM my_table x 
  JOIN my_table y 
    ON y.category = x.category 
   AND y.image_id >= x.image_id 
 GROUP 
    BY x.image_id 
HAVING COUNT(y.image_id) <=4 
 ORDER 
    BY category 
     , image_id DESC;
+----------+-----------+
| image_id | category  |
+----------+-----------+
|       30 | corporate |
|       27 | corporate |
|       25 | corporate |
|       15 | corporate |
|       35 | food      |
|       31 | food      |
|       24 | food      |
|       22 | food      |
|       36 | park      |
|       23 | park      |
|       19 | park      |
|       17 | park      |
|       37 | parties   |
|       28 | parties   |
|       20 | parties   |
|       13 | parties   |
|       29 | rides     |
|       26 | rides     |
|       21 | rides     |
|       14 | rides     |
|       32 | schools   |
|        9 | schools   |
|        6 | schools   |
|       34 | venue     |
|       33 | venue     |
|       10 | venue     |
|        7 | venue     |
+----------+-----------+
27 rows in set (0.00 sec)

【讨论】：

【解决方案2】：

此代码将检索每个类别的 4 张图像。如果你想检索最新的，那么只需在外部查询中添加排序。

    DB::table('gallery_images AS GI')
    ->where(function($query)
        {
            DB::table('tbl_dept_master AS GI2')
            ->select(DB::raw(count(1)))
            ->from('gallery_images As GI2')
            ->where('GI2.gallery','=','GI.gallery')
            ->where('GI2.title','>=','GI.title');
        })
    ->get();

如果需要更多帮助评论。希望这能解决您的问题。

【讨论】：