如何组合 2 个 MySQL 函数

Question

我有两个想要集成的 SQL 函数，能够通过单个 SQL 查询进行 prestashop 导出：

函数 1 连接来自不同表的数据。
函数 2 将多行转换为单行。

我无法让这些功能一起工作...让我描述一下这两个功能。

功能 1

SELECT a.id_product, a.ean13, a.weight, b.id_product, b.name, c.id_product, c.id_tab, c.content
FROM ps_product AS a
INNER JOIN ps_product_lang AS b ON b.id_product = a.id_product
INNER JOIN ps_extraproducttab_product_lang AS c ON c.id_product = a.id_product

这些 INNER JOINS 工作正常：

+------------+---------------+-------------+-----------+--------+-------------------+
| id_product | ean13         |   weight    |   name    | id_tab |      content      |
+------------+---------------+-------------+-----------+--------+-------------------+
|         11 | 0000000000001 | 1000.000000 | product_A |      1 | some ingredients  |
|         11 | 0000000000001 | 1000.000000 | product_A |      2 | some allergenes   |
|         12 | 0000000000002 | 1500.000000 | product_B |      1 | other ingredients |
|         12 | 0000000000002 | 1500.000000 | product_B |      2 | other allergenes  |
+------------+---------------+-------------+-----------+--------+-------------------+

但我想以某种方式转换 c。 第二个 INNER JOIN 使用在单个键 (id_product) 上有多行的表：

+--------+------------+---------+-------------------+
| id_Tab | id_product | id_lang |      content      |
+--------+------------+---------+-------------------+
|      1 |         11 |       1 | some ingredients  |
|      2 |         11 |       1 | some allergenes   |
|      1 |         12 |       1 | other ingredients |
|      2 |         12 |       1 | other allergenes  |
+--------+------------+---------+-------------------+

我想先合并这些行。 在表 'ps_extraproducttab_product_lang' 上运行第二个函数正是这样做的：

功能 2

SELECT t1.id_product, t1.content AS 'ingred', t2.content AS 'allerg'
FROM ps_extraproducttab_product_lang t1, ps_extraproducttab_product_lang t2
WHERE t1.id_product = t2.id_product
  AND t1.id_Tab = '1'
  AND t2.id_Tab = '2' 

它输出：

+------------+-------------------+------------------+
| id_product | ingred            | allerg           |
+------------+-------------------+------------------+
|         11 | some ingredients  | some allergenes  |
|         12 | other ingredients | other allergenes |
+------------+-------------------+------------------+

我使用了这个来源，由 Akina 提供：https://dba.stackexchange.com/questions/236692/combining-multiple-rows-into-a-single-row-with-multiple-columns （我仍然需要了解如何将此代码扩展到第 3 和第 4 个 id_Tab，尽管这不是我当前问题的主题）

我无法将上述内容整合到一个查询中，这会导致：

+------------+---------------+-------------+-----------+-------------------+-------------------+
| id_product | ean13         | weight      | name      | ingred            | allerg            |                  |
+------------+---------------+-------------+-----------+-------------------+-------------------+
|         11 | 0000000000001 | 1000.000000 | product_A | some ingredients  | some allergenes   |
|         12 | 0000000000002 | 1500.000000 | product_B | other ingredients | other allergenes  |
+------------+---------------+-------------+-----------+-------------------+-------------------+

您将如何构建单个 SQL 查询来获得上述结果？

感谢任何帮助！

Answer 1

如果在您的 Prestashop 平台上使用最新版本的 MySQL/MariaDB，请考虑多个 CTEs。请务必使用explicit joins（不像DBA SE 链接使用的那样隐含）并避免使用a, b, c table aliasing。将第 3 和第 4 个类别的自联接扩展到 ps_extraproducttab_product_lang。

WITH ew AS
  (SELECT p.id_product, p.ean13, p.weight, pl.name
   FROM ps_product AS p
   INNER JOIN ps_product_lang AS pl
      ON p.id_product = pl.id_product
  ), ia AS 
  (SELECT t1.id_product, t1.content AS 'ingred', t2.content AS 'allerg' 
        , t3.content AS 'thirdcat', t4.content AS 'fourthcat'
   FROM ps_extraproducttab_product_lang t1
   INNER JOIN  ps_extraproducttab_product_lang t2
      ON t1.id_product = t2.id_product 
     AND t1.id_Tab = '1' AND t2.id_Tab = '2' 
   INNER JOIN  ps_extraproducttab_product_lang t3
      ON t1.id_product = t3.id_product AND t3.id_Tab = '3'
   INNER JOIN  ps_extraproducttab_product_lang t4
      ON t1.id_product = t4.id_product AND t4.id_Tab = '4'
  )

SELECT ew.id_product, ew.ean13, ew.weight, ew.name
     , ia.ingred, ia.allerg, ia.thirdcat, ia.fourthcat
FROM ew
INNER JOIN ia
   ON ew.id_product = ia.id_product

对于早期版本的 MySQL（pre v8.0）或 MariaDB（pre v10.2），使用子查询：

SELECT ew.id_product, ew.ean13, ew.weight, ew.name
     , ia.ingred, ia.allerg, ia.thirdcat, ia.fourthcat
FROM 
  (SELECT p.id_product, p.ean13, p.weight, pl.name
   FROM ps_product AS p
   INNER JOIN ps_product_lang AS pl
      ON p.id_product = pl.id_product
  ) ew
INNER JOIN 
  (SELECT t1.id_product, t1.content AS 'ingred', t2.content AS 'allerg'
        , t3.content AS 'thirdcat', t4.content AS 'fourthcat'
   FROM ps_extraproducttab_product_lang t1
   INNER JOIN  ps_extraproducttab_product_lang t2
      ON t1.id_product = t2.id_product 
     AND t1.id_Tab = '1' AND t2.id_Tab = '2' 
   INNER JOIN  ps_extraproducttab_product_lang t3
      ON t1.id_product = t3.id_product AND t3.id_Tab = '3'
   INNER JOIN  ps_extraproducttab_product_lang t4
      ON t1.id_product = t4.id_product AND t4.id_Tab = '4'     
  ) ia
   ON ew.id_product = ia.id_product