SSM(三)Mybatis动态SQL

1.查询语句，where：

 <resultMap id="xxx" type="xx..Student" autoMapping="false">...</resultMap>
 <select id="findAll" resultMap="xxx">
     select * from student
     <where>
         <if test="stuNo!=null and stuNo!=''">and stuNo=#{stuNo}</if>
         <if test="stuName!=null and stuName!=''">and stuName like '%' #{stuName} '%'</if>
     </where>
 </select>

2.插入语句，trim：

 <insert id="saveAttendances">
         insert into tms_attendance
                 <trim prefix="(" suffixOverrides="," suffix=")">
                     <if test="at_tid != null">at_tid,</if>
                     <if test="at_labnum != null">at_labnum,</if>
                     ...
                 </trim>
             VALUES
         <trim prefix="(" suffixOverrides="," suffix=")">
             <if test="at_tid != null">#{at_tid},</if>
             <if test="at_labnum != null">#{at_labnum},</if>
             ...
         </trim>
     </insert>

3.修改语句，trim：

 <update id="editUserById" parameterType="cn.happy.entity.Smbms_user">
         update smbms_user
                 <trim prefix="set" suffixOverrides=",">
                     <if test="username !=null and username !=''">userName=#{username},</if>
                     <if test="userpassword !=null">userPassword=#{userpassword},</if>
                 </trim>
         where id=#{id}
     </update>

4.查询语句，foreach：

 <select id="findByList" resultType="Student">
     select * from student
     <if test="list.size>0">
         WHERE stuno in
         <foreach collection="list" open="(" close=")" separator="," item="myid">
             #{myid}
         </foreach>
     </if>
 </select>