I have 3 tables in SQL Server 2008 R2 that look like these:
A COMPANY may have many LSPs. An LSP may have many SERVICEs.
And I need to make sure that SERVICE_CODE uniquely identifies a SERVICE record within a COMPANY. In other words, COMPANY_ID + SERVICE_CODE should uniquely identify a SERVICE record in the entire system.
For example: COMPANY-A may NOT have 2 services (with 2 different SERVICE_IDs) with the same SERVICE_CODE. But COMPANY-A and COMPANY-B may both have 2 separate SERVICES (again, with different SERVICE_IDs) with SERVICE_CODE = "PREMIUM".
I need something like this:
alter table "SERVICE"
add constraint "SERVICE_Index01"
unique ("COMPANY_ID", "SERVICE_CODE")
But (obviously) this fails because the COMPANY_ID column is not in the SERVICE table.
Thanks in advance for any help.
To create a unique constraintIn Object Explorer, right-click the table to which you want to add a unique constraint, and select Design. On the Table Designer menu, select Indexes/Keys. In the Indexes/Keys dialog box, select Add.
A UNIQUE constraint can be referenced by a FOREIGN KEY constraint. When a UNIQUE constraint is added to an existing column or columns in the table, by default, the Database Engine examines the existing data in the columns to make sure all values are unique.
Yes you can do this from this example i didn't test it, but it should work.
You could use an indexed view as an external constraint:
CREATE VIEW dbo.CompanyServices
WITH SCHEMABINDING
AS
SELECT
c.COMPANY_ID,
s.SERVICE_CODE
FROM dbo.COMPANY c
INNER JOIN dbo.LSP l ON c.COMPANY_ID = l.COMPANY_ID
INNER JOIN dbo.SERVICE s ON l.LSP_ID = s.LSP_ID
GO
CREATE UNIQUE CLUSTERED INDEX UQ_CompanyServices
ON dbo.CompanyServices (COMPANY_ID, SERVICE_CODE);
The index will make sure there's no duplicates of (COMPANY_ID, SERVICE_CODE)
in your data.
Is each company limited to a single LSP? Is Service_Code unique (or could there be two service codes "PREMIUM" with different Service_IDs)?
CREATE TABLE dbo.Company
(
CompanyID INT PRIMARY KEY
-- , ...
);
CREATE TABLE dbo.LSP
(
LSPID INT PRIMARY KEY,
CompanyID INT FOREIGN KEY REFERENCES dbo.Company(CompanyID) -- UNIQUE?
-- , ...
);
CREATE TABLE dbo.Service
(
ServiceID INT PRIMARY KEY
-- , ...
);
CREATE TABLE dbo.LSP_Service
(
LSPID INT FOREIGN KEY REFERENCES dbo.LSP(LSPID),
ServiceID INT FOREIGN KEY REFERENCES dbo.Service(ServiceID),
PRIMARY KEY (LSPID, ServiceID)
);
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