Question

I have been thinking about a complicated view/query I need to create but I can’t seem to find a good (or working) solution to my problem. First I will give you a piece of my database structure to help explain my problem:

Every Agreement usually has 3 persons involved: a client, an endclient, and a contactperson. These role types are defined in the PersonAgreementInvolvementRole table. What I want is to create a view where I can get all three person names involved in the agreement, so something like this:

AgreementID  |  ClientName  |  EndClientName  |  ContactPersonName

          1  |  Company1    |     Company2    |     Smith

Because I need to go to the same (Person) table everytime to get the name of the person involved, I don’t know how I can do this best. I first tried something like this:

select ag.StartDate, ag.EndDate, ag.PriceRate, ag.TaskDescription, pc.Name as ClientName, pec.Name as EndClientName
from dbo.Agreement ag inner join dbo.PersonAgreementInvolvement pai
on ag.AgreementID = pai.AgreementID
inner join dbo.Person pc
on pai.PersonID = pc.PersonID
inner join dbo.PersonAgreementInvolvementRole pairc
on pai.PersonAgreementInvolvementRoleID = pairc.PersonAgreementInvolvementRoleID
inner join dbo.Person pec
on pai.PersonID = pec.PersonID
inner join dbo.PersonAgreementInvolvementRole pairec
on pai.PersonAgreementInvolvementRoleID = pairec.PersonAgreementInvolvementRoleID
where pairec.Value = 'Client'
and
pairc.Value = 'EndClient'

but that didn’t work (it returned no data at all), after that I tried a query with a union but that also didn’t work.

Any of you have an idea? More information can be provided if needed, just ask!

Example data:

I have an agreement (AgreementID = 1) with two persons involved. There is a person with the name “Google” which has the InvolvementRole “Client” and another person named “Microsoft” which has the InvolvementRole “EndClient”. What I would like to get from my query is the following:

AgreementID  -  Client  -  EndClient
-------------------- -----------------
1               Google     Microsoft

EDIT: SOLVED! Ultimately, this query did the job:

SELECT  ag.StartDate, ag.EndDate, ag.PriceRate, CAST( ag.TaskDescription AS VARCHAR(8000)),
        MIN(CASE WHEN pair.Value = 'Klant' THEN pc.Name END) as Klant, 
        MIN(CASE WHEN pair.Value = 'Eindklant' THEN pc.Name END) as Eindklant,
        MIN(CASE WHEN pair.Value = 'ContactPerson' THEN pc.Name END) as ContactPersonName
FROM dbo.Agreement ag
INNER JOIN dbo.PersonAgreementInvolvement pai 
ON ag.AgreementID = pai.AgreementID 
inner join dbo.PersonAgreementInvolvementRole pair
on pai.PersonAgreementInvolvementRoleID = pair.PersonAgreementInvolvementRoleID
LEFT JOIN dbo.Person pc
ON pai.PersonID = pc.PersonID 
GROUP BY ag.StartDate, ag.EndDate, ag.PriceRate, CAST( ag.TaskDescription AS VARCHAR(8000))

Thanks to everyone who helped me solve it! 🙂

Answer 1

If I understood your structure correctly, this should do the trick:

UPDATED QUERY

WITH PersonsInvolved AS
(
    SELECT  AgreementID,
            MIN(CASE WHEN pai.Value = 'Client' THEN pc.Name END) as ClientName,
            MIN(CASE WHEN pai.Value = 'EndClient' THEN pc.Name END) as EndClientName,
            MIN(CASE WHEN pai.Value = 'ContactPerson' THEN pc.Name END) as ContactPersonName
    FROM dbo.PersonAgreementInvolvement pai
    LEFT JOIN dbo.Person pc
    ON pai.PersonID = pc.PersonID
    GROUP BY AgreementID
)
SELECT  ag.StartDate, ag.EndDate, ag.PriceRate, ag.TaskDescription,
        pin.ClientName, pin.EndClientName, pin.ContactPersonName
FROM dbo.Agreement ag 
INNER JOIN PersonsInvolved pin
ON ag.AgreementID = pin.AgreementID