Plateforme Level Extreme
Abonnement
Profil corporatif
Produits & Services
Support
Légal
English
Get column from derived table
Message
 
 
À
11/06/2014 13:56:49
Information générale
Forum:
Visual FoxPro
Catégorie:
Autre
Versions des environnements
Visual FoxPro:
VFP 9 SP2
OS:
Windows Server 2012
Network:
Windows 2008 Server
Database:
MS SQL Server
Application:
Web
Divers
Thread ID:
01601694
Message ID:
01601728
Vues:
32
>>>>>>>>Does it make sense?
>>>>>>>
>>>>>>>You need a simple LEFT JOIN, e.g.
>>>>>>>select Cust.ID, Cust.Name, T.Descr as TypeDescr
>>>>>>>from Customer cust LEFT JOIN Types T ON Cust.Type_ID = T.Descr
>>>>>>
>>>>>>I tried it. LEFT JOIN creates a query where you have as many records for each record in CUSTOMER as there are TYPEs. Didn't work for me.
>>>>>
>>>>>Something doesn't make sense here.
>>>>>
>>>>>If type_ID in the Customer table is an FK and Type_ID in the Types table is primary key, then LEFT JOIN should only bring one row per customer with the type description.
>>>>>
>>>>>May be Type_ID is not the primary key in the Types table?
>>>>
>>>>Correct. See my reply to Rob.
>>>
>>>I saw the reply. So, which one of the descriptions per "type_id" do you want? Why do you allow duplicates in that lookup table? Sounds like a bad design.
>>
>>Now you are knocking my design; I am going to unfriend you :)
>>But seriously I see that I have a problem that I need to resolve.
>>Thank you.
>
>Key values should almost never be user editable. If the user needs to be able to change the type id, you should have another field in the database to act as the actual primary key.

The TYPE table has a PK field. My mistake was that I was storing in the Parent table the ID field instead of the PK field. So I decided to change the Parent table field from ID to the PK. This way if user chooses to have the same value in ID field for several records, it is his/her decision. But the query that I was looking to do will then work with LEFT JOIN. And I won't have to change the ID to unique field.
Just thought I would share this with you an Naomi (she will probably knock my design again :))
"The creative process is nothing but a series of crises." Isaac Bashevis Singer
"My experience is that as soon as people are old enough to know better, they don't know anything at all." Oscar Wilde
"If a nation values anything more than freedom, it will lose its freedom; and the irony of it is that if it is comfort or money that it values more, it will lose that too." W.Somerset Maugham
Précédent
Répondre
Fil
Voir

Click here to load this message in the networking platform