MySQL batch update

Method 1 ： use update combination case、then Realization

original SQL sentence

UPDATE baginfo_2021_09 
    SET channel_id = CASE id 
        WHEN 1 THEN 3 
        WHEN 2 THEN 4 
        WHEN 3 THEN 5 
    END, 
    stationId = CASE id 
        WHEN 1 THEN 6
        WHEN 2 THEN 7
        WHEN 3 THEN 8
    END
WHERE id IN (1,2,3)

mybatis How to write it

    <update id="updateBatchCaseThen" parameterType="java.util.List">
        update baginfo_2022_03
        <trim prefix="set" suffixOverrides=",">
            <trim prefix="clientId =case" suffix="end,">
                <foreach collection="list" item="i" index="index">
                    <if test="i.clientId!=null">
                        when id=#{i.id} then #{i.clientId}
                    </if>
                </foreach>
            </trim>
            <trim prefix="model_version =case" suffix="end,">
                <foreach collection="list" item="i" index="index">
                    <if test="i.model_version!=null">
                        when id=#{i.id} then #{i.model_version}
                    </if>
                </foreach>
            </trim>
            <trim prefix="create_time =case" suffix="end,">
                <foreach collection="list" item="i" index="index">
                    <if test="i.create_time!=null">
                        when id=#{i.id} then #{i.create_time}
                    </if>
                </foreach>
            </trim>
        </trim>
        where
        <foreach collection="list" separator="or" item="i" index="index">
            id=#{i.id}
        </foreach>
    </update>

Method 2 ： use foreach Cycle to achieve

mybatis How to write it

    <update id="batchUpdateBagInfo" parameterType="com.example.demo.entity.BagInfo">
        <foreach collection="list" item="item" index="index" open="" close="" separator=";">
            update baginfo_2022_03
            <set>
                <if test="item.clientId != null">
                    clientId = #{item.clientId},
                </if>
                <if test="item.model_version != null">
                    model_version = #{item.model_version},
                </if>
                <if test="item.create_time != null">
                    create_time = #{item.create_time},
                </if>
            </set>
            where id = #{item.id}
        </foreach>
    </update>

In this way ,yml The database configured in the file URL, Need to add &allowMultiQueries=true

Performance comparison

mysql Table data quantity ：2000w; Amount of data updated at one time ：1000

Update method	Total update time
Single loop update （for）	1-3s
Method 1	110ms-180ms
Method 2	110ms-180ms

Overall comparison , The slowest single loop update , Think about it . The method 1 And methods 2 The time taken is not much different . A higher number of batch updates , May lead to different results , There is no test here .