MyBatis-动态sql语句-if用法——MySQL系列学习笔记

Posted 2021-10-18 来老铁干了这碗代码

select

根据传入的参数来决定：如果用户名不为空，则对用户名进行模糊查询，如果邮箱不为空，则以邮箱为查询条件

    <select id="selectByUser" parameterType="com.tgb.mybatis.entity.SysUser" resultType="com.tgb.mybatis.entity.SysUser">
        select
            user_name "userName",
            user_password "userPassword",
            user_info "userInfo",
            head_img	"headImg",
            create_time "createTime"
        from
            sys_user
        where
            1=1
            <if test="userName != null and userName !=''">
              and user_name like CONCAT('%',#{userName},'%')
            </if>
            <if test="userEmail != null and userEmail != ''">
              and user_email =#{userEmail}
            </if>
    </select>

---

update

找到id为xxx这条数据，逐个属性判断，如果该属性不为空，则进行更新操作

    <update id="updateById">
        update sys_user
            SET
              <if test="userName != null and userName !=''">
                user_name = #{userName},
              </if>
              <if test="userPassword != null and userPassword !=''">
                user_password = #{userPassword},
              </if>
              <if test="userEmail != null and userEmail !=''">
                user_email = #{userEmail},
              </if>
              <if test="userInfo != null and userInfo !=''">
                user_info = #{userInfo},
              </if>
              <if test="headImg != null and headImg !=''">
                head_img = #{headImg},
              </if>
              <if test="createTime != null and createTime !=''">
                create_time =#{createTime},
              </if>
              id = #{id}
            where
                id = #{id}
    </update>

---

insert

    <insert id="insert">
        insert into sys_user(
          user_name,
          user_password,
          <if test="userEmail !=null and userEmail != ''">
              user_email,
          </if>
          user_info,
          head_img,
          create_time
        )
        VALUES
        (#{userName},
         #{userPassword},
        <if test="userEmail != null and userEmail !=''">
            user_email = #{userEmail},
        </if>
        #{userInfo},
        #{headImg, jdbcType=BLOB},
        #{createTime,jdbcType=TIMESTAMP})
    </insert>

---

关于where1=1的应用，参见我的这个博客——>一起去大厂系列】深入理解MySQL中where 1 = 1的用处