多表查詢 SQL

先建表User_Msg ，User_t ，User_tt
CREATE TABLE User_Msg (
 Sender_ID [varchar] (20)   NOT NULL ,
 Picker_ID [varchar] (20)   NOT NULL ,
 Msg [varchar] (200)   NOT NULL
)

CREATE TABLE  User_t (
 [User_id] [int] IDENTITY (1, 1) NOT NULL ,
 [User_Name] [varchar] (50) NOT NULL
)

CREATE TABLE  User_tt (
 [User_id] [int] primary key NOT NULL ,
 [User_Name] [varchar] (50) NOT NULL
)
執行SQL語句
==============================================================
select d.*,a.Picker_ID from User_Msg a,
 (select c.*,b.User_id from User_t b,User_Msg c
  where b.User_id=c.Sender_ID) d
where a.Picker_ID=d.User_id

===============================================================
select d.*,a.Picker_ID from User_Msg a,
 (select c.Sender_ID,c.Msg,b.User_id,b.user_name from User_t b,User_Msg c
  where b.User_id=c.Sender_ID) d
where a.Picker_ID=d.User_id