今天就跟大家聊聊有关使用MyBatis如何动态调用SQL标签，可能很多人都不太了解，为了让大家更加了解，小编给大家总结了以下内容，希望大家根据这篇文章可以有所收获。
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>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>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>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>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>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>看完上述内容，你们对使用MyBatis如何动态调用SQL标签有进一步的了解吗？如果还想了解更多知识或者相关内容，请关注编程网行业资讯频道，感谢大家的支持。
