Question

I’m no SQL expert so excuse if my question sounds silly.

I have a Multi-Lookup table:

ID ProID AmID

The ID is an identity column and auto-generates the ID on insert. The ProID and the AmID links to a Candidate table, on the ID column in that.

I need to create a View that will return the Firstname Lastname AS Pro and Firstname Lastname AS Am in a single view, along with the ID from the Candidate table.

ID Pro            ProID Am            AmID
1  Name Surname   1     Name Surname  2
2  Name Surname   3     Name Surname  78
etc

I created two separate select statements for both the pro and the am candidate, but don’t know how to merge them into a single statement?

SELECT  T2.[ID], 
        T2.[Firstname] + ' ' + T2.[Lastname] AS 'Pro'      
FROM [Teams] AS T1
INNER JOIN [Candidate] AS T2
    ON T1.ProID = T2.ID

SELECT  T2.[ID], 
        T2.[Firstname] + ' ' + T2.[Lastname] AS 'Am'       
FROM [Teams] AS T1
INNER JOIN [Candidate] AS T2
    ON T1.AmID = T2.ID

I looked this up, and it seems that I would need to do a RIGHT JOIN on this, but it screws up the results.

Is this scenario possible, or will I have to settle for two distinct calls to the SQL?

Answer 1

you need to basically join the table Candidate on your Teams table twice so you can get the equivalent value for each column.

SELECT  a.ID, b.ProID, c.AmID, 
        b.FirstName + ' ' + b.LastName as ProName, 
        c.FirstName + ' ' + c.LastName as AmName   
FROM    Teams a
        INNER JOIN candidate b
            ON a.ProID = b.ID
        INNER JOIN candidate c
            ON a.AmID = c.ID

If one of the columns is nullable, LEFT JOIN is needed than INNER JOIN so non-matching values will still be on the list of result.

To fully gain knowledge about joins, kindly visit the link below:

• Visual Representation of SQL Joins

To create VIEW

CREATE VIEW viewName
AS
    SELECT  a.ID, b.ProID, c.AmID, 
            b.FirstName + ' ' + b.LastName as ProName, 
            c.FirstName + ' ' + c.LastName as AmName   
    FROM    Teams a
            INNER JOIN candidate b
                ON a.ProID = b.ID
            INNER JOIN candidate c
                ON a.AmID = c.ID

• TSQL View