Couple foreignKey reference a table with couple PrimaryKey - sql-server

Question

I have two tables
CREATE TABLE [dbo].[Customer]
(
[SourceID] [int] NOT NULL,
[ID_N] [bigint] NOT NULL,
[RegionCode] [varchar](1) NOT NULL,
[NSID] [int] NOT NULL,
CONSTRAINT [Pk_Customer] PRIMARY KEY CLUSTERED
([RegionCode] ASC, [ID_N] ASC)
)
CREATE TABLE [dbo].[Order]
(
[Reference][nvarchar](50) NOT NULL,
[SourceID] [int] NOT NULL,
[ID_N] [nvarchar](50) NULL,
[RegionCode] [varchar](1) NULL,
[Customer_ID_N] [bigint] NULL,
CONSTRAINT [PK_Order] PRIMARY KEY CLUSTERED
([Reference] ASC)
)
I want to put (CustomemrID_N,RegionCode) as a Foreign Key reference to the Customer table.
Alter table [dbo].[Order]
ADD CONSTRAINT FK_Order_Customer FOREIGN KEY (Customer_ID_N,RegionCode)
REFERENCES[dbo].[Customer](ID_N,RegionCode)
but i get this error :
There are no primary or candidate keys in the referenced table 'dbo.Customer' that match the referencing column list in the foreign key 'FK_Order_Customer'.

Answer 1

There are so many problems with your attempt... Most are typographical.
Firstly this statement:
CREATE TABLE [dbo].[Customer](
[SourceID] [int] NOT NULL,
[ID_N] [bigint] NOT NULL,
[RegionCode] [varchar](1) NOT NULL,
[NSID] [int] NOT NULL,
CONSTRAINT [Pk_Customer] PRIMARY KEY CLUSTERED
([RegionCode] ASC, [ID_N] ASC)
This is missing a right parenthesis ()) at the end of the statement.
Then the next statement:
CREATE TABLE [dbo].[Order](
[Reference][nvarchar](50) NOT NULL,
[SourceID] [int] NOT NULL,
[ID_N] [nvarchar](50) NULL,
[RegionCode] [varchar](1) NULL,
[Customer_ID_N] [bigint] NULL,
CONSTRAINT [PK_Order] PRIMARY KEY CLUSTERED
([Reference] ASC)
This too, isn't valid, there is also a missing right parenthesis.
Your last statement is also, not valid:
Alter table [dbo].[Order]
ADD CONSTRAINT FK_Order_CustomerFOREIGN KEY ([Customer_ID_N],RegionCode)
REFERENCES[dbo].[Customer](ID_N,RegionCode)
CONSTRAINT FK_Order_CustomerFOREIGN KEY should be CONSTRAINT FK_Order_Customer FOREIGN KEY; notice the space between FK_Order_Customer and `FOREIGN.
Once we fix that we get yet something like this:
CREATE TABLE [dbo].[Customer](
[SourceID] [int] NOT NULL,
[ID_N] [bigint] NOT NULL,
[RegionCode] [varchar](1) NOT NULL,
[NSID] [int] NOT NULL,
CONSTRAINT [Pk_Customer] PRIMARY KEY CLUSTERED
([RegionCode] ASC, [ID_N] ASC))
GO
CREATE TABLE [dbo].[Order](
[Reference][nvarchar](50) NOT NULL,
[SourceID] [int] NOT NULL,
[ID_N] [nvarchar](50) NULL,
[RegionCode] [varchar](1) NULL,
[Customer_ID_N] [bigint] NULL,
CONSTRAINT [PK_Order] PRIMARY KEY CLUSTERED
([Reference] ASC))
GO
Alter table [dbo].[Order]
ADD CONSTRAINT FK_Order_Customer FOREIGN KEY ([Customer_ID_N],RegionCode)
REFERENCES[dbo].[Customer](ID_N,RegionCode)
Note, when you run that, you get the error you have above. That's because your PK is defined as [RegionCode] ASC, [ID_N] ASC not ID_N,RegionCode. So let's fix that as swap the foreign key around...
Alter table [dbo].[Order]
ADD CONSTRAINT FK_Order_Customer FOREIGN KEY (RegionCode,[Customer_ID_N])
REFERENCES[dbo].[Customer](RegionCode, ID_N)
And now it works.
Address the typographical errors, then read the error; it was telling you the problem.