技術標籤：mybatismysql

• 問題

  由於巢狀結果方式會導致結果集被摺疊，因此分頁查詢的結果在摺疊後總數會減少

  <resultMap id="baseResultMap" type="com.jia.Student">
      <id column="id" property="id"/>
      <result column="name" property="name"/>
      <result column="gender"
   
   property="gender"/>
      <collection property="bookList" ofType="com.jia.Book">
          <result column="book_id" property="id"/>
          <result column="student_id" property="studentId"/>
          <result column
   
  ="amount" property="amount"/>
      </collection>
  </resultMap>
  
  <select id="getStudent" resultMap="baseResultMap">
      SELECT
          Student.id,
          Student.`name`,
          Student.gender,
          book.id book_id,
          book.student_id,
          book.
   
  amount
      FROM
          student
          left join book on book.student_id=student.id
      WHERE
          student.is_delete=0
      limit 
      	#{pageNumber} ,#{pageSize}
  </select>
  

• 解決方法

  使用collection裡的select定義查詢，條件是上層student的id

  執行過程是，先執行getStudent的查詢，將學生全都查詢出來並進行分頁，這種情況下分頁是沒問題的，然後再去查詢每個學生對應的多條書本資訊，走collection裡的select查詢，他會自己查詢book資訊封裝到每個對應的student中，完成查詢。

  <resultMap id="baseResultMap" type="com.jia.Student">
      <id column="id" property="id"/>
      <result column="name" property="name"/>
      <result column="gender" property="gender"/>
      <collection property="bookList" ofType="com.jia.Book" select="selectBook" column="id">
          <result column="book_id" property="id"/>
          <result column="student_id" property="studentId"/>
          <result column="amount" property="amount"/>
      </collection>
  </resultMap>
  
  <select id="getStudent" resultMap="baseResultMap">
      SELECT
          Student.id,
          Student.`name`,
          Student.gender
      FROM
          student
      WHERE
          student.is_delete=0
      limit 
      	#{pageNumber} ,#{pageSize}
  </select>
  
  <select id="selectBook" resultType="com.jia.Book">
      select * from  book where book.student_id=#{id}
  </select>