Is it possible to have two primary keys on the same table?
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No. A table can have only one primary key.
However, that primary key can consist of two columns. For example, consider this table of DatabaseProducts:
Company Product Release IBM DB2 5 Microsoft SQL Server 7.0 Microsoft Access 97 Oracle Oracle 8 Sybase ASE 12.5
As it stands, you could define this table with:
create table DatabaseProducts ( Company varchar(20) , Product varchar(20) , Release varchar(10) , constraint DatabaseProductPK primary key (Company, Product) )
If you wanted the table to contain both Microsoft SQL Server 7.0 and Microsoft SQL Server 2000, then the primary key would have to include the Release column as well.
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