mybatis的动态增删改查

 1、动态SQL片段
 通过SQL片段达到代码复用
         <!-- 动态条件分页查询 -->
         <sql id="sql_count">
                 select count(*)
         </sql>
         <sql id="sql_select">
                 select *
         </sql>
         <sql id="sql_where">
                 from icp
                 <dynamic prepend="where">
                         <isNotEmpty prepend="and" property="name">
                                 name like '%$name$%'
                         </isNotEmpty>
                         <isNotEmpty prepend="and" property="path">
                                 path like '%path$%'
                         </isNotEmpty>
                         <isNotEmpty prepend="and" property="area_id">
                                 area_id = #area_id#
                         </isNotEmpty>
                         <isNotEmpty prepend="and" property="hided">
                                 hided = #hided#
                         </isNotEmpty>
                 </dynamic>
                 <dynamic prepend="">
                         <isNotNull property="_start">
                                 <isNotNull property="_size">
                                         limit #_start#, #_size#
                                 </isNotNull>
                         </isNotNull>
                 </dynamic>
         </sql>
         <select id="findByParamsForCount" parameterClass="map" resultClass="int">
                 <include refid="sql_count"/>
                 <include refid="sql_where"/>
         </select>
         <select id="findByParams" parameterClass="map" resultMap="icp.result_base">
                 <include refid="sql_select"/>
                 <include refid="sql_where"/>
         </select>

 2、数字范围查询
 所传参数名称是捏造所得，非数据库字段，比如_img_size_ge、_img_size_lt字段
                         <isNotEmpty prepend="and" property="_img_size_ge">
                                 <![CDATA[
                                 img_size >= #_img_size_ge#
                         ]]>
                         </isNotEmpty>
                         <isNotEmpty prepend="and" property="_img_size_lt">
                                 <![CDATA[
                                 img_size < #_img_size_lt#
                         ]]>
                         </isNotEmpty> 

 多次使用一个参数也是允许的
                         <isNotEmpty prepend="and" property="_now">
                                 <![CDATA[
                                             execplantime >= #_now#
                                      ]]>
                         </isNotEmpty>
                         <isNotEmpty prepend="and" property="_now">
                                 <![CDATA[
                                             closeplantime <= #_now#
                                      ]]>
                         </isNotEmpty>

 3、时间范围查询
                         <isNotEmpty prepend="" property="_starttime">
                                 <isNotEmpty prepend="and" property="_endtime">
                                         <![CDATA[
                                         createtime >= #_starttime#
                                         and createtime < #_endtime#
                                  ]]>
                                 </isNotEmpty>
                         </isNotEmpty> 

 4、in查询
                         <isNotEmpty prepend="and" property="_in_state">
                                 state in ('$_in_state$')
                         </isNotEmpty>

 5、like查询
                         <isNotEmpty prepend="and" property="chnameone">
                                 (chnameone like '%$chnameone$%' or spellinitial like '%$chnameone$%')
                         </isNotEmpty>
                         <isNotEmpty prepend="and" property="chnametwo">
                                 chnametwo like '%$chnametwo$%'
                         </isNotEmpty> 

 6、or条件
                         <isEqual prepend="and" property="_exeable" compareValue="N">
                                 <![CDATA[
                                 (t.finished='11'    or t.failure=3)
                         ]]>
                         </isEqual>

                         <isEqual prepend="and" property="_exeable" compareValue="Y">
                                 <![CDATA[
                                 t.finished in ('10','19') and t.failure<3
                         ]]>
                         </isEqual>

 7、where子查询
                         <isNotEmpty prepend="" property="exprogramcode">
                                 <isNotEmpty prepend="" property="isRational">
                                         <isEqual prepend="and" property="isRational" compareValue="N">
                                                 code not in
                                                 (select t.contentcode
                                                 from cms_ccm_programcontent t
                                                 where t.contenttype='MZNRLX_MA'
                                                 and t.programcode = #exprogramcode#)
                                         </isEqual>
                                 </isNotEmpty>
                         </isNotEmpty>

         <select id="findByProgramcode" parameterClass="string" resultMap="cms_ccm_material.result">
                 select *
                 from cms_ccm_material
                 where code in
                 (select t.contentcode
                 from cms_ccm_programcontent t
                 where t.contenttype = 'MZNRLX_MA'
                 and programcode = #value#)
                 order by updatetime desc
         </select>

 9、函数的使用
         <!-- 添加 -->
         <insert id="insert" parameterClass="RuleMaster">
                 insert into rulemaster(
                 name,
                 createtime,
                 updatetime,
                 remark
                 ) values (
                 #name#,
                 now(),
                 now(),
                 #remark#
                 )
                 <selectKey keyProperty="id" resultClass="long">
                         select LAST_INSERT_ID()
                 </selectKey>
         </insert>
         <!-- 更新 -->
         <update id="update" parameterClass="RuleMaster">
                 update rulemaster set
                 name = #name#,
                 updatetime = now(),
                 remark = #remark#
                 where id = #id#
         </update>

 10、map结果集
         <!-- 动态条件分页查询 -->
         <sql id="sql_count">
                 select count(a.*)
         </sql>
         <sql id="sql_select">
                 select a.id                vid,
                 a.img             imgurl,
                 a.img_s         imgfile,
                 b.vfilename vfilename,
     b.name            name,
                 c.id                sid,
                 c.url             url,
                 c.filename    filename,
                 c.status        status
         </sql>
         <sql id="sql_where">
                 From secfiles c, juji b, videoinfo a
                 where
                 a.id = b. videoid
                 and b.id = c.segmentid
                 and c.status = 0
                 order by a.id asc,b.id asc,c.sortnum asc
                 <dynamic prepend="">
                         <isNotNull property="_start">
                                 <isNotNull property="_size">
                                         limit #_start#, #_size#
                                 </isNotNull>
                         </isNotNull>
                 </dynamic>
         </sql>
         <!-- 返回没有下载的记录总数 -->
         <select id="getUndownFilesForCount" parameterClass="map" resultClass="int">
                 <include refid="sql_count"/>
                 <include refid="sql_where"/>
         </select>
         <!-- 返回没有下载的记录 -->
         <select id="getUndownFiles" parameterClass="map" resultClass="java.util.HashMap">
                 <include refid="sql_select"/>
                 <include refid="sql_where"/>
         </select>

 11、trim
  trim是更灵活的去处多余关键字的标签，他可以实践where和set的效果。

  where例子的等效trim语句：
 Xml代码
 <!-- 查询学生list，like姓名，=性别 -->
 <select id="getStudentListWhere" parameterType="StudentEntity" resultMap="studentResultMap">
     SELECT * from STUDENT_TBL ST
     <trim prefix="WHERE" prefixOverrides="AND|OR">
         <if test="studentName!=null and studentName!='' ">
             ST.STUDENT_NAME LIKE CONCAT(CONCAT('%', #{studentName}),'%')
         </if>
         <if test="studentSex!= null and studentSex!= '' ">
             AND ST.STUDENT_SEX = #{studentSex}
         </if>
     </trim>
 </select> 

 set例子的等效trim语句：
 Xml代码
 <!-- 更新学生信息 -->
 <update id="updateStudent" parameterType="StudentEntity">
     UPDATE STUDENT_TBL
     <trim prefix="SET" suffixOverrides=",">
         <if test="studentName!=null and studentName!='' ">
             STUDENT_TBL.STUDENT_NAME = #{studentName},
         </if>
         <if test="studentSex!=null and studentSex!='' ">
             STUDENT_TBL.STUDENT_SEX = #{studentSex},
         </if>
         <if test="studentBirthday!=null ">
             STUDENT_TBL.STUDENT_BIRTHDAY = #{studentBirthday},
         </if>
         <if test="classEntity!=null and classEntity.classID!=null and classEntity.classID!='' ">
             STUDENT_TBL.CLASS_ID = #{classEntity.classID}
         </if>
     </trim>
     WHERE STUDENT_TBL.STUDENT_ID = #{studentID};
 </update>   

 12、choose (when, otherwise)
          有时候我们并不想应用所有的条件，而只是想从多个选项中选择一个。MyBatis提供了choose 元素，按顺序判断when中的条件出否成立，如果有一个成立，则choose结束。当choose中所有when的条件都不满则时，则执行 otherwise中的sql。类似于Java 的switch 语句，choose为switch，when为case，otherwise则为default。
          if是与(and)的关系，而choose是或（or）的关系。

          例如下面例子，同样把所有可以限制的条件都写上，方面使用。选择条件顺序，when标签的从上到下的书写顺序：
 Xml代码
 <!-- 查询学生list，like姓名、或=性别、或=生日、或=班级，使用choose -->
 <select id="getStudentListChooseEntity" parameterType="StudentEntity" resultMap="studentResultMap">
     SELECT * from STUDENT_TBL ST
     <where>
         <choose>
             <when test="studentName!=null and studentName!='' ">
                     ST.STUDENT_NAME LIKE CONCAT(CONCAT('%', #{studentName}),'%')
             </when>
             <when test="studentSex!= null and studentSex!= '' ">
                     AND ST.STUDENT_SEX = #{studentSex}
             </when>
             <when test="studentBirthday!=null">
                 AND ST.STUDENT_BIRTHDAY = #{studentBirthday}
             </when>
             <when test="classEntity!=null and classEntity.classID !=null and classEntity.classID!='' ">
                 AND ST.CLASS_ID = #{classEntity.classID}
             </when>
             <otherwise>   

             </otherwise>
         </choose>
     </where>
 </select>