select总结

select [all | distinct] -- 去重可选
colunmname1 [as aliasname, colunmname2 as aliasname2,...] 
from tablename [as tableAliasName]
[left | right | inner join tablename on joinconditions] -- 联接查询
[where filtercondition] -- 过滤条件
[group by colunmname | aliasname -- 分组
having filter condition] -- 分组的过滤条件
[order by ASC | DESC] -- 排序
[limit startindex, pagesize] --分页

注：

[] 表示可选