mybatis 实现批量更新的三种方式

注：Mybatis实现批量更新有三种方式，分别是使用foreach标签、使用SQL的case when语句和使用动态SQL的choose语句。具体实现方法如下：

1：使用foreach标签

<update id="batchUpdate" parameterType="java.util.List">
  update user set name=#{name}, age=#{age} where id=#{id}
  <foreach collection="list" item="item" index="index" separator=";">
    update user set name=#{item.name}, age=#{item.age} where id=#{item.id}
  </foreach>
</update>

2：使用SQL的case when语句

<update id="batchUpdate" parameterType="java.util.List">
  update user set name = case id
    <foreach collection="list" item="item" index="index" separator=" ">
      when #{item.id} then #{item.name}
    </foreach>
  end,
  age = case id
    <foreach collection="list" item="item" index="index" separator=" ">
      when #{item.id} then #{item.age}
    </foreach>
  end
  where id in
  <foreach collection="list" item="item" index="index" open="(" close=")" separator=",">
    #{item.id}
  </foreach>
</update>

3：使用动态SQL的choose语句

<update id="batchUpdate" parameterType="java.util.List">
  <foreach collection="list" item="item" index="index" separator=";">
    <choose>
      <when test="item.name != null and item.age != null">
        update user set name=#{item.name}, age=#{item.age} where id=#{item.id}
      </when>
      <when test="item.name != null">
        update user set name=#{item.name} where id=#{item.id}
      </when>
      <when test="item.age != null">
        update user set age=#{item.age} where id=#{item.id}
      </when>
    </choose>
  </foreach>
</update>