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  • Mybatis里Mapper.xml加强

    批量插入
    insert into user(user_id,name) values (1,'test0'),(2,'test1');

    <!-- 批量插入 -->
    <insert id="batchInsert" parameterType="java.util.List">
    insert into
    user(
    user_id,name
    )
    values
    <foreach collection="list" item="item" index="index" separator=",">
    (#{item.userId},#{item.name})
    </foreach>
    </insert>

    批量删除
    delete from user where user_id in(1,2);
    <!-- 批量删除 -->
    <delete id="batchDel" parameterType="java.util.List">
    delete from user
    where
    user_id in
    <foreach item="item" index="index" collection="list" open="(" separator="," close=")">
    #{item}
    </foreach>
    </delete>

    批量更新
    ①:循环更新,连接数据库N次,效率低
    update user set name = 'test0' where user_id=1;update user set name = 'test1' where user_id =2;

    <!-- 批量更新 -->
    <update id="batchUpdate" parameterType="java.util.List">
    <foreach collection="list" item="item" index="index" open="" close="" separator=";">
    update user
    <set>
    name=#{name}
    </set>
    where user_id = #{item.userId}
    </foreach>
    </update>

    ②:循环更新,连接数据库一次,效率较高(case when的两种写法)
    写法一:
    update user set name = case user_id when 1 then 'test0' when 2 then 'test1' else name end where user_id in(1,2)

    <update id="batchUpdate" parameterType="java.util.List">
    update user set name=
    <foreach collection="list" item="item" index="index" separator=" " open="case user_id" close="end">
    when #{item.userId} then #{item.name}
    </foreach>
    where user_id in
    <foreach collection="list" index="index" item="item" separator="," open="(" close=")">
    #{item.user_id}
    </foreach>
    </update>

    写法二:
    update user set name = case when user_id = 1 then 'test0' when user_id = 2 then 'test1' else name end where user_id in(1,2)

    <update id="batchUpdate" parameterType="java.util.List">
    update user
                     set name =
                  <foreach collection="list" item="item" index="index" separator=" " open="case " close="else name end">
    when user_id = #{item.userId} then #{item.name}
    </foreach>
                 where id in
                     <foreach collection="list" index="index" item="item" separator="," open="(" close=")">
                     #{item.userId}
                     </foreach>
    </update>

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  • 原文地址:https://www.cnblogs.com/guoyinghome/p/10901420.html
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