<?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.xiaKangan.mapper.EmpMapper">
<!--    SQL片段的重复使用-->
    <!-- 将SQL代码放入sql标签中，可以在其他增删改查操作中引入id实现复用-->
    <sql id="sqlSyntax">
        select * from emp where name like concat('%',#{name},'%') and gender= #{gender} and
            entrydate between #{begin} and #{end} order by update_time desc
    </sql>
    <select id="cSearch" resultType="com.xiaKangan.pojo.Emp">
        -- 引入SQL片段
        <include refid="sqlSyntax"/>
--         select * from emp where name like concat('%',#{name},'%') and gender= #{gender} and
--                                 entrydate between #{begin} and #{end} order by update_time desc
    </select>

<!--    动态SQL条件查询-->
    <select id="conditionSearch" resultType="com.xiaKangan.pojo.Emp">
        select *
        from emp
--      where标签当有至少一个条件成立时，生成SQLwhere语句，并且自动修正SQL语句
        <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SQL更新数据-->
    <update id="update2">
        update emp
        set
        -- 将SQL语句里面多余的语法结构删除掉，避免语法错误
        -- trim 标签中还有 prefixOverrides 删除语法中的前缀多余部分
        -- 在if语句的外层添加set标签也能纠正语法
        <trim suffixOverrides=",">
             <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>
        </trim>
        <where>
            id = #{id}
        </where>
    </update>

<!--    批量删除员工信息(18,19,21)-->
    <delete id="deleteByIds">
        delete from emp where id in
        -- collection 遍历的集合
        -- item 遍历出来的元素
        -- separater 分隔符
        -- open 遍历开始前的符号
        -- close 遍历结束的符号
        <foreach collection="ids" item="id" separator="," open="(" close=")">
            #{id}
        </foreach>
    </delete>


</mapper>

XML动态SQL图片文件