Select data from two rows of the same table

Question

I have a table called TransferRequest with two columns that are (receivingPrison, currentPrison). They both reference a table Prison with columns (prisonID, location). I need to have some sort of join to display the 'location' of both prison eg. Result: "Washington", "New York". I know to get the location from one table I can do:

SELECT Prison.location  
FROM Prison
JOIN TransferRequest
ON Prison.prisonID = TransferRequest.currentPrison;

And:

SELECT Prison.location  
FROM Prison
JOIN TransferRequest
ON Prison.prisonID = TransferRequest.receivingPrison;

But I'm not sure how to do a SELECT for two of the same type of items from the same type of table. What would I do to get this table? (Headers: Current Location, Receiving Location).

Answer 1

Maybe I'm missing something but if you just want to get the location names for the current and receiving prisons you could get them by joining the prison table twice:

SELECT 
  rec_prison.location as 'Recieving Location',
  cur_prison.location as 'Current Location'
FROM TransferRequest tr
INNER JOIN Prison rec_prison 
  ON rec_prison.prisonID = tr.receivingPrison 
INNER JOIN Prison cur_prison 
  ON cur_prison.prisonID = tr.currentPrison;

Sample SQL Fiddle

Answer 2

A correlated subquery could do it:

SELECT P1.location AS location1

, (SELECT Prison.location  
FROM Prison
JOIN TransferRequest
ON Prison.prisonID = TransferRequest.receivingPrison ) AS location2

FROM Prison P1
JOIN TransferRequest T1
   ON P1.prisonID = T1.currentPrison;

Answer 3

You can use this:

SELECT (SELECT       prison.Location
        FROM         TransferRequest tr
        INNER JOIN   Prison prison ON tr.reciveingPrisonID = prison.prisonID
        WHERE        tr.reciveingPrisonID = 1) AS'Recieving Location',
       (SELECT       prison.Location
        FROM         TransferRequest tr
        INNER JOIN   Prison prison ON tr.currentPrisonID = prison.prisonID
        WHERE        tr.currentPrisonID = 4) as 'Current Location'

See this here-> http://sqlfiddle.com/#!3/9aac5/9

Hope this helps!!!