You are a database developer of a Microsoft SQL Server 2012 database.
The database contains a table named Customers that has the following definition:
You need to ensure that the CustomerId column in the Orders table contains only values that exist in
the CustomerId column of the Customer table.
Which Transact-SQL statement should you use?
A.
ALTER TABLE Orders
ADD CONSTRAINT FX_Orders_CustomerID FOREIGN KEY (CustomerId) REFERENCES
Customer (CustomerId)
B.
ALTER TABLE Customer
ADD CONSTRAINT FK_Customer_CustomerID FOREIGN KEY {CustomerID) REFERENCES
Orders (CustomerId)
C.
ALTER TABLE Orders
ADD CONSTRAINT CK_Crders_CustomerID
CHECK (CustomerId IN (SELECT CustomerId FROM Customer))
D.
ALTER TABLE Customer
ADD OrderId INT NOT NULL;
ALTER TABLE Customer
ADD CONSTRAINT FK_Customer_OrderID FOREIGN KEY (CrderlD) REFERENCES Orders
(CrderlD);
E.
ALTER TABLE Orders
ADD CONSTRAINT PK Orders CustomerId PRIMARY KEY (CustomerID)
Explanation:
http://msdn.microsoft.com/en-us/library/ms189049.aspx
you need foreign key constraint, so ‘a’, ‘b’ and ‘d’ to consider. ‘d’ has no sense, and ‘b’ is wrong. ‘a’ is correct answer to create foreign key constraint.
Why not ‘b’? – because you create foreign key constraint in table that it belongs to. Owner of fk is ‘Orders’ table and only references ‘Customers’ table, so you need to alter ‘Orders’ table.
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