Question

此示例仅是我的数据库的架构。我有下表叫做食谱：

id | author_name | recipe1_id | recipe2_id | recipe3_id

所有食谱都与recipes_ingredients表有关：

id | recipe_id | ingredient1 | ingredient2 | ingredient3

现在我在recipe1_id上对recipe3_id进行三次JOINS，如下所示：

SELECT recipe1.ingredient1 as recipe1ingredient1, recipe1.ingredient2 as recipe1ingredient2, recipe1.ingredient3 as recipe1ingredient3, [...]
FROM recipes
INNER JOIN recipe recipe1 ON (recipes.recipe1_id = recipes.id)
INNER JOIN recipe recipe2 ON (recipes.recipe2_id = recipes.id)
INNER JOIN recipe recipe3 ON (recipes.recipe3_id = recipes.id)

要将3个食谱映射到MyBatis中的一个bean，我有三个resultsMaps，它们将每个食谱映射到包含3种成分的食谱对象（recipe1，recipe2，recipe3）。

但是：我希望将食谱列入清单。我怎么能实现这一目标？

PS：可以肯定的是，我在表食谱和表recipes_ingredients中只有3个实体。这永远不会改变，所以我没有理由把它放在n：m表中。

Answer 1

我认为这会奏效。

<resultMap id="recipe1" type="recipe1">
 ...
</resultMap>

<resultMap id="recipe2" type="recipe2">
 ...
</resultMap>

<resultMap id="recipe3" type="recipe3">
 ...
</resultMap>

<select id="getRecipes" parameterType="list" resultMap="recipe1, recipe2, recipe3">
   SELECT recipe1.ingredient1 as recipe1ingredient1, recipe1.ingredient2 as recipe1ingredient2, recipe1.ingredient3 as recipe1ingredient3, [...]
   FROM recipes
   INNER JOIN recipe recipe1 ON (recipes.recipe1_id = recipes.id)
   INNER JOIN recipe recipe2 ON (recipes.recipe2_id = recipes.id)
   INNER JOIN recipe recipe3 ON (recipes.recipe3_id = recipes.id)
</select>

来源：MyBatis multiple resultsets

如何处理链接同一实体的几个列

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