MySQL 计数来自多个表的列。按主要 ID 对结果进行分组

Question

我有以下 3 个 MySQL 表：

products

| id | name      | comment_count |
|----|-----------|---------------|
| 1  | Product A | 10            |
| 2  | Product B | 20            |
| 3  | Product C | 30            |

products_views

| product_id | pv_count | pv_date       |
| -----------|-------|------------|
| 1          | 10    | 2015-01-01 |
| 1          | 10    | 2015-01-02 |
| 1          | 10    | 2015-01-03 |
| 2          | 20    | 2015-01-01 |
| 2          | 20    | 2015-01-02 |
| 2          | 20    | 2015-01-03 |
| 3          | 30    | 2015-01-01 |
| 3          | 30    | 2015-01-02 |
| 3          | 30    | 2015-01-03 |

products_likes

| product_id | pl_count | pl_date       |
| -----------|-------|------------|
| 1          | 10    | 2015-01-01 |
| 1          | 10    | 2015-01-02 |
| 1          | 10    | 2015-01-03 |
| 2          | 20    | 2015-01-01 |
| 2          | 20    | 2015-01-02 |
| 2          | 20    | 2015-01-03 |
| 3          | 30    | 2015-01-01 |
| 3          | 30    | 2015-01-02 |
| 3          | 30    | 2015-01-03 |

我想将 products.comment_count + product_views.count + product_likes.count 按 products.id 分组相加，其中 product_views.pv_date 和 product_likes.pl_date 在 [= 之间20=] 和 2015-01-03。按 total.

排序我想要的是：

| product_id | total |
| -----------|-------|
| 3          | 210   |
| 2          | 140   |
| 1          | 70    |

Answer 1

试试这个查询

SELECT 
   p.product_id, 
  (p.comment_count + SUM(pv.count) + SUM(pl.count)) AS total
 FROM products p
 JOIN products_views pv ON( p.product_id = pv.product_id)
 JOIN products_likes pl ON( p.product_id = pl.product_id)
 WHERE pl.date BETWEEN '2015-01-01' AND '2015-01-03'
  AND pv.date BETWEEN '2015-01-01' AND '2015-01-03'
 GROUP BY p.product_id   
 ORDER BY total DESC

Answer 2

select p.product_id, sum(p.comment_count) + sum(v.count) + sum(l.count) as total from products p join products_views v on p.product_id = v.product_id join products_likes l on p.product_id = l.product_id group by p.product_id
where l.date between '2015-01-01' and '2015-01-03'
order by total desc

试试这个

Answer 3

SELECT 
    (products.comment_count+products_views.pv_count+products_likes.pl_count) AS    product_count
    FROM products 
    INNER JOIN products_views.product_id=products.id
    INNER JOIN products_likes.product_id=products.id
    WHERE  (product_views.pv_date BETWEEN dateVal AND dateVal) 
    AND (products_likes.pl_date BETWEEN dateVal AND dateVal) 
   GROUP BY     products.id
   ORDER BY  product_count

Answer 4

在加入之前执行计数 "per table" 否则你运行获得比应有的更大结果的风险，因为加入可以成倍增加行数。此外，由于某些产品可能不存在于喜欢或观看中，因此建议对两个 "derived tables" 进行左外部连接。

SELECT
      p.product_id
    , (IFNULL(p.comment_count,0) + IFNULL(pv.view_count, 0) + IFNULL(pl.like_count, 0)) AS total
FROM products p
      LEFT OUTER JOIN (
            SELECT
                  product_id
                , SUM(`count`) AS view_count
            FROM products_views
            WHERE `date` BETWEEN '2015-01-01' AND '2015-01-03'
            GROUP BY
                  product_id
      ) pv ON p.product_id = pv.product_id
      LEFT OUTER JOIN (
            SELECT
                  product_id
                , SUM(`count`) AS like_count
            FROM products_likes
            WHERE `date` BETWEEN '2015-01-01' AND '2015-01-03'
            GROUP BY
                  product_id
      ) pl ON p.product_id = pl.product_id
GROUP BY
      p.product_id
ORDER BY
      total DESC

顺便说一句：date 和 count 是大多数 SQL 方言中的保留字；将列命名为 date 或 count 不是一个好主意；使用更多的东西，例如date_entered、date_created、view_count、like_count 等

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