MySQL SELECT来自OpenCarts数据库的重复行 [英] MySQL SELECT Duplicated rows from OpenCarts DataBase

问题描述

只需与OpenCarts DB一起玩，看看我是否可以学习一些东西. 如果我使用以下 SELECT ，结果将返回重复的行:

Just playing with OpenCarts DB to see if I can lear something. If I use the following SELECT the result returns duplicated rows:

SELECT DISTINCT
p.product_id AS pid,
p.model AS modelo,
SUBSTRING(p.model,1,25) AS substr_modelo,
p.image AS foto,
p.price AS preco,
pd.name AS nome,
cd.name AS category
FROM product p
LEFT JOIN product_description pd ON p.product_id = pd.product_id
LEFT JOIN product_to_category p2c ON p.product_id = p2c.product_id
LEFT JOIN category_description cd ON p2c.category_id = cd.category_id
WHERE pd.name LIKE _utf8 'laser%' collate utf8_unicode_ci
ORDER BY p.product_id DESC

请注意，即使使用 DISTINCT ，它也是重复的，但是如果我添加 GROUP BY p.product_id ，它将停止重复行.这是最好的解决方案吗?

Note that even using DISTINCT it is duplicated, but if I add an GROUP BY p.product_id it stops duplicating the rows. Is it the best solution?

推荐答案

DISTINCT删除重复的整行.

使用GROUP BY p.product_id每个产品ID显示一个1行.

Use GROUP BY p.product_id to display one 1 row per product id.

注意:如果您按product_id分组，则如果您具有多个产品描述，多个类别或多个类别描述，则查询将为每个查询返回一个随机行.使用 MIN() 或<一个href ="http://dev.mysql.com/doc/refman/5.0/en/group-by-functions.html#function_max" rel ="nofollow"> MAX() 函数来检索单个ID ，或使用 GROUP_CONCAT() 函数以检索所有描述.

Note: If you group by product_id, if you have multiple product description's, multiple categories, or multiple category description's The query will return a random row for each. Use the MIN() or MAX() functions to retrieve single ID's, or use the GROUP_CONCAT() function to retrieve all the description.

SELECT
  p.product_id AS pid,
  p.model AS modelo,
  SUBSTRING(p.model,1,25) AS substr_modelo,
  p.image AS foto,
  p.price AS preco,
  GROUP_CONCAT(pd.name) AS nome,
  GROUP_CONCAT(cd.name) AS category
FROM product p
  LEFT JOIN product_description pd ON p.product_id = pd.product_id
  LEFT JOIN product_to_category p2c ON p.product_id = p2c.product_id
  LEFT JOIN category_description cd ON p2c.category_id = cd.category_id
  WHERE pd.name LIKE _utf8 'laser%' collate utf8_unicode_ci
GROUP BY p.product_id
ORDER BY p.product_id DESC

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