Sql join, 2 tables, same fields

Question

I have 2 tables. To simplify:

Table 1, users:

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userId int, userName nvarchar(50)

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Table 2 , messages:

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msgId int, msgFrom int,

Answer 1

Join users table twice with different aliases. First join to from column, second to to column.

select m.*, u1.userName as Sender, u2.userName as Recipient 
from tabMessages as m 
  inner join tabUsers as u1 
    on u1.userId=m.msgFrom 
  inner join tabUsers as u2 
    on u2.userId=m.msgTo 
where m.msgId = @someParameter;

Answer 2

You need to join onto tabUsers twice. One to get the sender, one to get the recipient:

SELECT m.*, f.userName as Sender, t.userName as Recipient 
FRPOM tabMessages AS m
    INNER JOIN tabUsers AS f on m.msgFrom = f.userId
    INNER JOIN tabUsers AS t on m.msgTo = t.userId 
WHERE m.msgId = @someParameter;

Answer 3

Did you try a UNION??

http://www.w3schools.com/sql/sql_union.asp