SELECT連表查詢重複字段

連表查詢不用SELECT * 直接用 SELECT FIELD 列字段，錯誤：兩個表出現重複的兩個字段userId：

Cause: java.sql.SQLIntegrityConstraintViolationException: Column 'userId' in field list is ambiguous

eg: 兩個表blog和user連表查詢：

select
	userId,publishDateTime,blogId,blogTitle,blogContent
from blog
	inner join user on blog.userId=user.userId
order by
	publishDateTime desc limit #{page},#{limit}

（1）、第一種，只保留其中一個字段：

select
	blog.userId,publishDateTime,blogId,blogTitle,blogContent
from blog
	inner join user on blog.userId=user.userId
order by
	publishDateTime desc limit #{page},#{limit}

（2）、第二種，保留兩個字段，起別名：

select
	blog.userId as userId,user.userId as uid,publishDateTime,blogId,blogTitle,blogContent
from blog
	inner join user on blog.userId=user.userId
order by
	publishDateTime desc limit #{page},#{limit}

  保證結果有自己起的別名屬性字段

（3）、第三種，給表起別名：

select
	bb.userId,uu.userId as uid,publishDateTime,blogId,blogTitle,blogContent
from blog bb
	inner join user uu on bb.userId=uu.userId
order by
	publishDateTime desc limit #{page},#{limit}
	
或者加上as：

select
	bb.userId,uu.userId as uid,publishDateTime,blogId,blogTitle,blogContent
from blog as bb
	inner join user as uu on bb.userId=uu.userId
order by
	publishDateTime desc limit #{page},#{limit}