create table 聊天记录表(id int identity(1,1),userid varchar(15),content nvarchar(1000))
create table 用户表(userid varchar(15),username nvarchar(20),address nvarchar(100))
declare @userid varchar(15)
set @userid='...'
select * from 聊天记录表 a,用户表 b where a.userid=b.userid and userid=@userid