select
     t1.*
    ,concat(replace(substr(result,instr(result,‘"url":"‘) +7,instr(result,‘"}‘)-instr(result,‘"url":"‘) -7),‘https://‘,‘http://‘),‘@1500h‘)  as temp_image -- json数据截取
from (
    SELECT 
         t.*
        ,concat(substring_index(substring_index(t.image_file,‘"},{"‘, b.help_topic_id + 1), ‘"},{"‘, -1),‘"}‘) as result -- 列转行
    FROM (
        SELECT
             a.id
            ,a.image_file -- json array string
        FROM table_a a
        where length(a.image_file) > 3
        limit 10,1
    ) t
    join (
        select 0 as help_topic_id union all
        select 1 as help_topic_id union all
        select 2 as help_topic_id union all
        select 3 as help_topic_id union all
        select 4 as help_topic_id union all
        select 5 as help_topic_id union all
        select 6 as help_topic_id union all
        select 7 as help_topic_id union all
        select 8 as help_topic_id union all
        select 9 as help_topic_id
    ) b 
        ON b.help_topic_id <  ((LENGTH(t.image_file) - LENGTH(REPLACE(t.image_file, ‘"},{"‘, ‘‘)))/5 + 1)
    order by result
) t1
;