sql执行顺序:from on join where group by having select distinct union order by
别名的使用:
SELECT download_type as type,count(*) from download
GROUP BY type
正常来说 group by 先 于select 执行,是找不到type这个字段的。mysql里做了优化 再group by 和order by 里可以使用 type 这个别名,相当于使用了 download_type
标签:顺序,group,别名,sql,download,type,select From: https://www.cnblogs.com/tiancai/p/17603107.html