Microsoft SQL Server
- Getting started with Microsoft SQL Server
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- Advanced options
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- Add foreign key on existing table
- Adding foreign key relationship on existing table
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Microsoft SQL Server Foreign Keys Add foreign key on existing table
Example
FOREIGN KEY columns with constraint can be added on existing tables that are still not in relationship. Imagine that we have Company and Employee tables where Employee table don't have CompanyId column. ALTER TABLE statement enables you to add new column with foreign key constraint that references some other table and primary key in that table:
alter table Employee
add CompanyId int foreign key references Company(CompanyId)
