数据库关联查询

一、这两种写法事等效的：第二种写法大的效率更高
select p.* from sys_post p, sys_dept d
where d.dept_id = #{deptId} and p.remark = d.dept_name

SELECT * from sys_post where sys_post.remark
=(select dept_name from sys_dept where dept_id=#{deptId});