本文轉自：http://tiannanyi.blog.163.com/blog/static/18735934420153345927979/
轉載請註明出處--
1、動態SQL片段
通過SQL片段達到代碼複用
<!-- 動態條件分頁查詢 --> <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$%' </isNotEmpty> <isNotEmpty prepend="and" property="area_id"> area_id = #area_id# </isNotEmpty> <isNotEmpty prepend="and" property="hided"> hided = #hided# </isNotEmpty> </dynamic> <dynamic prepend=""> <isNotNull property="_start"> <isNotNull property="_size"> limit #_start#, #_size# </isNotNull> </isNotNull> </dynamic> </sql> <select id="findByParamsForCount" parameterClass="map" resultClass="int"> <include refid="sql_count"/> <include refid="sql_where"/> </select> <select id="findByParams" parameterClass="map" resultMap="icp.result_base"> <include refid="sql_select"/> <include refid="sql_where"/> </select>
2、數字範圍查詢
所傳參數名稱是捏造所得，非數據庫字段，比如_img_size_ge、_img_size_lt字段
<isNotEmpty prepend="and" property="_img_size_ge"> <![CDATA[ img_size >= #_img_size_ge# ]]> </isNotEmpty> <isNotEmpty prepend="and" property="_img_size_lt"> <![CDATA[ img_size < #_img_size_lt#]]> </isNotEmpty>
多次使用一個參數也是允許的
<isNotEmpty prepend="and" property="_now"> <![CDATA[ execplantime >= #_now# ]]> </isNotEmpty> <isNotEmpty prepend="and" property="_now"> <![CDATA[ closeplantime <= #_now#]]> </isNotEmpty>
3、時間範圍查詢
<isNotEmpty prepend="" property="_starttime"> <isNotEmpty prepend="and" property="_endtime"> <![CDATA[createtime >= #_starttime# and createtime < #_endtime#]]> </isNotEmpty> </isNotEmpty>
4、in查詢
<isNotEmpty prepend="and" property="_in_state">
state in ('$_in_state$')
</isNotEmpty>5、like查詢
<isNotEmpty prepend="and" property="chnameone"> (chnameone like '%$chnameone$%' or spellinitial like '%$chnameone$%') </isNotEmpty> <isNotEmpty prepend="and" property="chnametwo"> chnametwo like '%$chnametwo$%' </isNotEmpty>
6、or條件
<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子查詢
<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、函數的使用
<!-- 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結果集
<!-- 動態條件分頁查詢 --> <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> <!-- 返回沒有下載的記錄總數 --> <select id="getUndownFilesForCount" parameterClass="map" resultClass="int"> <include refid="sql_count"/> <include refid="sql_where"/> </select> <!-- 返回沒有下載的記錄 --> <select id="getUndownFiles" parameterClass="map" resultClass="java.util.HashMap"> <include refid="sql_select"/> <include refid="sql_where"/> </select>
11、trim
trim是更靈活的去處多餘關鍵字的標籤，他可以實踐where和set的效果。
where例子的等效trim語句：
Xml代碼
<!-- 查詢學生list，like姓名，=性別 -->
<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語句：
Xml代碼
<!-- 更新學生信息 -->
<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)
有時候我們並不想應用所有的條件，而只是想從多個選項中選擇一個。MyBatis提供了choose 元素，按順序判斷when中的條件出否成立，如果有一個成立，則choose結束。當choose中所有when的條件都不滿則時，則執行 otherwise中的sql。類似於Java 的switch 語句，choose爲switch，when爲case，otherwise則爲default。
if是與(and)的關係，而choose是或（or）的關係。
例如下面例子，同樣把所有可以限制的條件都寫上，方面使用。選擇條件順序，when標籤的從上到下的書寫順序：Xml代碼
<!-- 查詢學生list，like姓名、或=性別、或=生日、或=班級，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>