mybatis 学习整理

一、查询表中的某个字段

dao/mapper

String getSalt(@Param("userName") String userName);

  <select id="getSalt" resultType="string" parameterType="map">
    select salt from com_manager
    where user_name = #{userName,jdbcType=VARCHAR} limit 1
  </select>

二、只取部分值，不定义新DTO

dao/mapper :

List<Map<String, Object>> selectPartBook();

service:

List<Map<String, Object>> map = bookMapper.selectPartBook();

<!-- 查询语句 -->
<select id="selectPartBook" resultMap="PartBookMap">
    select book_id, book_name, author from book
</select>