我有一个规范化的数据库，我正在尝试使用JOIN和GROUP_CONCAT从多个表返回数据。
问题：行与GROUP_CONCAT重复。我不能使用DISTINCT，因为某些数据（成分mfr）确实需要重复。
这是我当前的查询和数据库结构（SQL Fiddle）：
SELECT recipe.*,
GROUP_CONCAT(recipe_detail.ingredient_id) AS iid,
GROUP_CONCAT(ingredient.name) AS iname,
GROUP_CONCAT(ingredient_mfr.abbr) AS mabbr,
GROUP_CONCAT(recipe_tag.name) AS tag
FROM recipe
LEFT JOIN recipe_detail
ON recipe.id = recipe_detail.recipe_id
LEFT JOIN ingredient
ON recipe_detail.ingredient_id = ingredient.id
LEFT JOIN ingredient_mfr
ON ingredient.mfr_id = ingredient_mfr.id
LEFT JOIN recipe_tagmap
ON recipe.id = recipe_tagmap.recipe_id
LEFT JOIN recipe_tag
ON recipe_tagmap.tag_id = recipe_tag.id
WHERE recipe.user_id = 1
GROUP BY recipe.id
recipe
+------------+------------+-----------+
| id | name | user_id |
+============+============+===========+
| 1 | Test123 | 1 |
+------------+------------+-----------+
| 2 | Test456 | 1 |
+------------+------------+-----------+
| 3 | Test789 | 1 |
+------------+------------+-----------+
recipe_detail
+------------+---------------+
| recipe_id | ingredient_id |
+============+===============+
| 1 | 193 |
+------------+---------------+
| 1 | 194 |
+------------+---------------+
| 2 | 16 |
+------------+---------------+
| 3 | 277 |
+------------+---------------+
ingredient
+------------+---------------+---------+
| id | name | mfr_id |
+============+===============+=========+
| 16 | Gin | 4 |
+------------+---------------+---------+
| 193 | Fig | 3 |
+------------+---------------+---------+
| 194 | Tea | 3 |
+------------+---------------+---------+
| 277 | Nut | 2 |
+------------+---------------+---------+
ingredient_mfr
+------------+------------+
| id | abbr |
+============+============+
| 2 | TFA |
+------------+------------+
| 3 | FA |
+------------+------------+
| 4 | LOR |
+------------+------------+
recipe_tag
+------------+------------+
| id | name |
+============+============+
| 1 | one |
+------------+------------+
| 2 | two |
+------------+------------+
| 3 | three |
+------------+------------+
| 4 | four |
+------------+------------+
| 5 | five |
+------------+------------+
| 6 | six |
+------------+------------+
| 7 | seven |
+------------+------------+
| 8 | eight |
+------------+------------+
| 9 | nine |
+------------+------------+
recipe_tagmap
+------------+---------------+---------+
| id | recipe_id | tag_id |
+============+===============+=========+
| 1 | 1 | 1 |
+------------+---------------+---------+
| 2 | 1 | 2 |
+------------+---------------+---------+
| 3 | 1 | 3 |
+------------+---------------+---------+
| 4 | 2 | 4 |
+------------+---------------+---------+
| 5 | 2 | 5 |
+------------+---------------+---------+
| 6 | 2 | 6 |
+------------+---------------+---------+
| 7 | 3 | 7 |
+------------+---------------+---------+
| 8 | 3 | 8 |
+------------+---------------+---------+
| 9 | 3 | 9 |
+------------+---------------+---------+
使用我当前的查询，我的结果如下所示：
+------+---------+--------------+----------- ----+---------------+------------------+
| id | name | iid | iname | mabbr | tag |
+======+=========+==============+================+===============+==================+
| 1 | Test123 | 193,193,193, | Fig, Fig, Fig, | FA, FA, FA, | one, two, three, |
| | | 194,194,194 | Tea, Tea, Tea | FA, FA, FA | one, two, three |
+------+---------+--------------+----------------+---------------+------------------+
| 2 | Test456 | 16,16,16 | Gin, Gin, Gin | LOR, LOR, LOR | four, five six |
+------+---------+--------------+----------------+---------------+------------------+
| 3 | Test789 | 277,277,277 | Nut, Nut, Nut | TFA, TFA, TFA | seven,eight,nine |
+------+---------+--------------+----------------+---------------+------------------+
我希望我的结果如下：
+------+---------+--------------+----------- ----+---------------+------------------+
| id | name | iid | iname | mabbr | tag |
+======+=========+==============+================+===============+==================+
| 1 | Test123 | 193, 194 | Fig, Tea | FA, FA | one, two, three, |
+------+---------+--------------+----------------+---------------+------------------+
| 2 | Test456 | 16 | Gin | LOR | four, five six |
+------+---------+--------------+----------------+---------------+------------------+
| 3 | Test789 | 277 | Nut | TFA | seven,eight,nine |
+------+---------+--------------+----------------+---------------+------------------+
如您所见，多个标签的存在会导致配料数据重复。多种成分的存在导致标签复制。我曾试图使用DISTINCT，但有时我会有多种成分，其中每一种都会返回它自己的“mabbr”，这可能与它的其他成分相同（参见预期结果的第一行）。使用DISTINCT，它只返回该“mabbr”的一个实例。
我可以对我的查询进行更改以实现我想要做的事情吗？
您可以通过将tag分组提取到其自己的子查询来解决此问题：
SELECT
recipe.*,
GROUP_CONCAT(recipe_detail.ingredient_id) AS iid,
GROUP_CONCAT(ingredient.name) AS iname,
GROUP_CONCAT(ingredient_mfr.abbr) AS mabbr,
(
SELECT GROUP_CONCAT(recipe_tag.name)
FROM recipe_tag
INNER JOIN recipe_tagmap
ON recipe_tagmap.tag_id = recipe_tag.id
WHERE recipe_tagmap.recipe_id = recipe.id
) AS tag
FROM recipe
LEFT JOIN recipe_detail
ON recipe.id = recipe_detail.recipe_id
LEFT JOIN ingredient
ON recipe_detail.ingredient_id = ingredient.id
LEFT JOIN ingredient_mfr
ON ingredient.mfr_id = ingredient_mfr.id
WHERE recipe.user_id = 1
GROUP BY recipe.id
（例如fiddle）
在执行GROUP_CONCAT时添加distinct将为您提供唯一值。
SELECT recipe.*,
GROUP_CONCAT(distinct recipe_detail.ingredient_id) AS iid,
GROUP_CONCAT(distinct ingredient.name) AS iname,
GROUP_CONCAT(distinct ingredient_mfr.abbr) AS mabbr,
GROUP_CONCAT(distinct recipe_tag.name) AS tag
FROM recipe
LEFT JOIN recipe_detail
ON recipe.id = recipe_detail.recipe_id
LEFT JOIN ingredient
ON recipe_detail.ingredient_id = ingredient.id
LEFT JOIN ingredient_mfr
ON ingredient.mfr_id = ingredient_mfr.id
LEFT JOIN recipe_tagmap
ON recipe.id = recipe_tagmap.recipe_id
LEFT JOIN recipe_tag
ON recipe_tagmap.tag_id = recipe_tag.id
WHERE recipe.user_id = 1
GROUP BY recipe.id