Question

mybatis的怎么在select标签里引用where标签

Answer 1

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<sql id="query_user_where">
<!-- 如果 userQueryVo中传入查询条件，再进行sql拼接-->
<!-- test中userCustom.username表示从userQueryVo读取属性值-->
<if test="userCustom!=null">
<if test="userCustom.username!=null and userCustom.username!=''">
and username like '%${userCustom.username}%'
</if>
<if test="userCustom.sex!=null and userCustom.sex!=''">
and sex = #{userCustom.sex}
</if>
<!-- 根据id集合查询用户信息 -->
<!-- 最终拼接的效果：
SELECT id ,username ,birthday FROM USER WHERE username LIKE '%小明%' AND id IN (16,22,25)
collection：集合的属性
open：开始循环拼接的串
close：结束循环拼接的串
item：每次循环取到的对象
separator：每两次循环中间拼接的串
-->
<foreach collection="ids" open=" AND id IN ( " close=")" item="id" separator=",">
#{id}
</foreach>
<!--
SELECT id ,username ,birthday FROM USER WHERE username LIKE '%小明%' AND (id = 16 OR id = 22 OR id = 25)
<foreach collection="ids" open=" AND ( " close=")" item="id" separator="OR">
id = #{id}
</foreach>
-->
<!-- 还有很的查询条件 -->
</if>
</sql>
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</span><select id="findUserList" parameterType="userQueryVo" resultType="user">
select id,username,birthday from user
<!-- where标签相当 于where关键字，可以自动去除第一个and -->
<where>
<!-- 引用sql片段，如果sql片段和引用处不在同一个mapper必须前边加namespace -->
<include refid="query_user_where"></include>
<!-- 下边还有很其它的条件 -->
<!-- <include refid="其它的sql片段"></include> -->
</where>
</select>