SELECT语句返回用指定的条件在一个数据库中查询的结果，返回的结果被看作记录的集合。语法：SELECT [predicate] { * | table.* | [table.]field1 [AS alias1] [， [table.]field2 [AS alias2] [， ...]]} FROM tableexpression [， ...] [IN externaldatabase] [WHERE... ] [GROUP BY... ] [HAVING... ] [ORDER BY... ] [WITH OWNERACCESS OPTION]