MyBatis动态SQL标签用法

1、动态SQL片段

通过SQL片段达到代码复用

<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

多次使用一个参数也是允许的

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

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

<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>
        
        <update id="update" parameterClass="RuleMaster">
                update rulemaster set
                name = #name#,
                updatetime = now(),
                remark = #remark#
                where id = #id#
        </update>

10、map结果集

<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>

<select id="getUndownFilesForCount" parameterClass="map" resultClass="int">
<include refid="sql_count"/>
<include refid="sql_where"/>
</select>

<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

<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

<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

<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>