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想象一个食谱数据库。共有三个表：

tbl_recipes、tbl_recipe_ingredients 和 tbl_ingredients。

成分可以是蔬菜或肉类。（ingtype 字段）

我需要有两个查询，一个是提取所有包含蔬菜和肉类的食谱，另一个是只提取蔬菜。

我一直在尝试这个查询，但它没有返回准确的结果数量。

SELECT DISTINCT tbl_recipes.title
FROM tbl_recipe_ingredients
INNER JOIN tbl_recipes ON tbl_recipe_ingredients.recipe_id = tbl_recipes.id
INNER JOIN tbl_ingredients ON tbl_recipe_ingredients.ingredient_id = tbl_ingredients.id
WHERE tbl_ingredients.ingtype = 'vegetable'
GROUP BY tbl_recipes.id
HAVING COUNT( DISTINCT tbl_ingredients.ingtype ) = 1

另一件不起作用的事情是，如果我将 Count 更改为 = 2（意味着每种成分类型中的一种或多种），我将得不到任何结果。

我认为这是 Top N 类型查询的一种变体，但我无法看到这个问题出在哪里。

我将不胜感激任何帮助。

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2 回答 2

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SELECT DISTINCT tbl_recipes.id,GROUP_CONCAT(DISTINCT tbl_ingredients.ingtype ORDER BY tbl_ingredients.ingtype) AS VEGETABLE_TYPE
FROM tbl_recipe_ingredients
   INNER JOIN tbl_recipes ON tbl_recipe_ingredients.recipe_id = tbl_recipes.id
   INNER JOIN tbl_ingredients ON tbl_recipe_ingredients.ingredient_id = tbl_ingredients.id
GROUP BY tbl_recipes.id
HAVING VEGETABLE_TYPE= 'vegetable'
于 2014-02-14T18:17:55.997 回答
1

要获得那些只有蔬菜的标题，您可以使用COUNTwith执行以下操作CASE：

SELECT DISTINCT tbl_recipes.title
FROM tbl_recipe_ingredients
   INNER JOIN tbl_recipes ON tbl_recipe_ingredients.recipe_id = tbl_recipes.id
   INNER JOIN tbl_ingredients ON tbl_recipe_ingredients.ingredient_id = tbl_ingredients.id
GROUP BY tbl_recipes.id
HAVING COUNT( CASE WHEN tbl_ingredients.ingtype = 'vegetable' THEN 1 END ) = COUNT(1)

这会计算所有与蔬菜相同的成分类型，并与总计数进行比较——如果它们相同，则匹配。

然后要得到既有蔬菜又有肉的，这应该有效：

SELECT DISTINCT tbl_recipes.title
FROM tbl_recipe_ingredients
   INNER JOIN tbl_recipes ON tbl_recipe_ingredients.recipe_id = tbl_recipes.id
   INNER JOIN tbl_ingredients ON tbl_recipe_ingredients.ingredient_id = tbl_ingredients.id
WHERE tbl_ingredients.ingtype IN ('vegetable','meat')
GROUP BY tbl_recipes.id
HAVING COUNT( DISTINCT tbl_ingredients.ingtype ) = 2

第二个查询中的WHERE子句可能不需要 - 取决于您是否有其他成分类型。这会计算DISTINCT成分类型以确保它等于 2。

于 2013-05-30T18:29:54.003 回答