mybatis利用collection传递多参数子查询

mybatis利用collection传递多参数子查询的步骤如下：
1.在mapper.xml文件中定义一个select语句，其中使用了collection标签来传递多个参数，例如：

<select id="selectByCollection" parameterType="java.util.Map" resultMap="BaseResultMap">
    select * from table_name where column in
    <foreach collection="list" item="item" open="(" separator="," close=")">
        #{item}
    </foreach>
</select>

2.在Java代码中调用该select语句，并传递一个Map类型的参数，其中包含一个名为list的List类型的值，例如：

List<Integer> list = new ArrayList<>();
list.add(1);
list.add(2);
Map<String, Object> map = new HashMap<>();
map.put("list", list);
List<Table> result = sqlSession.selectList("selectByCollection", map);

这样就可以利用collection传递多个参数进行子查询了。

相关问题

mybatis参数传递collection

Mybatis中，可以使用`collection`标签将集合类型的参数传递给SQL语句。具体的用法如下：

1. 定义一个包含集合类型参数的方法，例如：

public List<User> selectUsersByIds(@Param("ids") List<Integer> ids);

2. 在Mapper.xml文件中编写对应的SQL语句，例如：

<select id="selectUsersByIds" resultType="User">
   select * from user where id in
   <foreach item="item" index="index" collection="ids" open="(" separator="," close=")">
      #{item}
   </foreach>
</select>

在这个例子中，使用`collection`标签将集合类型的参数`ids`传递给SQL语句中的`in`条件中。`open`属性表示在集合的第一个元素前插入的字符串，`separator`属性表示在每个元素之间需要插入的字符串，`close`属性表示在集合的最后一个元素之后需要插入的字符串。

3. 在调用方法时，传入集合类型的参数即可：

List<Integer> ids = Arrays.asList(1, 2, 3);
List<User> users = userMapper.selectUsersByIds(ids);

在这个例子中，将一个包含3个元素的List作为参数传递给`selectUsersByIds`方法，Mybatis会自动将其转换为SQL语句中的`in`条件，查询出对应的用户列表。

mybatis collection 子查询

MyBatis allows you to perform collection subqueries, which can be useful when you need to retrieve related data for a collection of records. Collection subqueries are typically used in scenarios where you have a one-to-many or many-to-many relationship between tables.

To implement a collection subquery in MyBatis, you can use the `<collection>` element within your result mapping. Here's an example:

<resultMap id="userMap" type="User">
  <id property="id" column="user_id" />
  <result property="name" column="user_name" />
  <collection property="orders" ofType="Order">
    <id property="id" column="order_id" />
    <result property="product" column="product_name" />
  </collection>
</resultMap>

In this example, we have a `User` object that has a collection of `Order` objects. The `User` object has an `id` and a `name`, while the `Order` object has an `id` and a `product`. The `collection` element is used to define the mapping for the collection property (`orders`) of the `User` object.

To perform the collection subquery, you can use the `<select>` element with a nested `<collection>` element in your SQL statement. Here's an example:

<select id="getUserWithOrders" resultMap="userMap">
  SELECT u.id AS user_id, u.name AS user_name,
         o.id AS order_id, o.product AS product_name
  FROM users u
  INNER JOIN orders o ON u.id = o.user_id
  WHERE u.id = #{userId}
</select>

In this example, we join the `users` and `orders` tables on the `user_id` column and retrieve the relevant columns for both the `User` and `Order` objects. The `<collection>` element is used to map the query results to the collection property (`orders`) of the `User` object.

You can then use this mapping and SQL statement in your MyBatis mapper interface to retrieve a `User` object with its associated `Order` objects.

I hope this explanation helps! Let me know if you have any further questions.