How can I add a foreign key reference ?

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How can I add foreign Key reference using Desgin or Query, it doesn't matter just i need to understand it very good . i will be so glad for an explanation about it .

I have Order table and has (CustomerFirstName, CustomerLastName,Id,RecivedAt) columns and i have also OrderItem table and has (Id,ItemNr, and OrderId which should be reference to Id in Order Table ) columns

I can't get that until now very well .

What I have tried:

here is the Query but please explain it clear .

Alter table .....
add constraint tbl..._...._FK FOREIGN KEY (...) references tbl(....)

Posted 29-Aug-19 0:57am

Abdalla Ben Omran

Updated 29-Aug-19 7:13am

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3 solutions

Solution 2

Google is your friend.

Goole search for "SQL Server what is a foreign key"[^]

Posted 29-Aug-19 1:03am

#realJSOP

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CHill60 · Accepted Answer · 2019-08-29T01:03:00

Solution 1

Please do your own research - this is a quick answers forum.

The following free resources will explain Foreign Keys fully:
Essential Guide to SQL Server FOREIGN KEY Constraint[^]
The Essential Guide To SQL Foreign Key Constraint[^]

Posted 29-Aug-19 1:03am

CHill60

Member 11511491 · Accepted Answer · 2019-08-29T07:13:00

Solution 4

Following is the explanation your query. Hopes this help you to get an idea.

According to your requirement OrderItem table is the parent table. Order table is the child table. So Order table is reference with the OrderItem table. Following is the querry for this purpose.

Alter table Order
add constraint tbl..._...._FK(constraint name) FOREIGN KEY (Id) references (OrderItem)

Posted 29-Aug-19 7:13am

Member 11511491

Updated 29-Aug-19 7:14am

v2

Comments

CHill60 30-Aug-19 3:42am

Completely the opposite of what is required. OrderItem is a child of Order so the FK should be in the OrderItem table - insisting that an Order must exist before an item can be added to it

[no name] 30-Aug-19 4:35am

yes Chill60 you have right .

[no name] 30-Aug-19 4:37am

Member 11511491, thanks for your answer but i meant the opposite (OrderItem) reference with Order