Primary keys - the basics
Single-column primary keys
Multicolumn primary keys
Auto-increment columns and sequences
Instruction
Nice. As you can see, there are quite a few ways of auto-numbering in databases. Some of them only use IDENTITY (e.g. SQL Server), other take AUTO_INCREMENT (e.g. MySQL), and there are also such databases which only have sequences (e.g. PostgreSQL). So, each time you work with a new database, read the documentation and check which of the options are available.
Exercise
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