mybatis动态sql语法

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.qvfan.mybatistest.mapper.EmpMapper">
    <sql id="commonSelect">
        select id,username,password,name,gender,image,job,entrydate,dept_id,create_time,update_time
        from emp
    </sql>
    <!-- id和mapper接口中的方法名保持一致  resultType为单条记录所封装的类型 -->
    <select id="list" resultType="com.qvfan.mybatistest.pojo.Emp">
        <include refid="commonSelect"></include>
        <where>
          <if test="name != null">
            name like concat('%', #{name}, '%')
          </if>
          <if test="gender != null">
              and gender = #{gender}
          </if>
          <if test="begin != null and end != null">
              and entrydate between #{begin} and #{end}
          </if>
        </where>
        order by update_time desc
    </select>
    <!--  动态更新员工信息  -->
    <update id="update2" >
        update emp
        <set>
            <if test="username != null">username =#{username},</if>
            <if test="name != null">name=#{name},</if>
            <if test="gender != null">gender=#{gender},</if>
            <if test="image != null">image=#{image},</if>
            <if test="job != null">job=#{job},</if>
            <if test="entrydate != null">entrydate=#{entrydate},</if>
            <if test="deptId != null">dept_id=#{deptId},</if>
            <if test="updateTime != null">update_time=#{updateTime}</if>
        </set>
        where id = #{id};
    </update>
    <!--
        批量删除员工
        collection : 遍历的集合
        item : 遍历出来的元素
        separator : 分隔符
        open :  遍历开始前拼接的sql片段
        close : 遍历结束后拼接的sql片段
     -->
    <delete id="deleteById">
        delete from emp  where id in
          <foreach collection="ids" item="id" separator="," open="(" close=")">
                #{id}
          </foreach>
    </delete>
</mapper>

以上

查询使用了sql include 将通用的抽离出来,用where if 来进行判断 从而实现 动态sql

更新使用了set if

删除使用了foreach 来进行批量删除