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  3. Introduction to Relational Databases in SQL
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Add a SERIAL surrogate key

Since there's no single column candidate key in professors (only a composite key candidate consisting of firstname, lastname), you'll add a new column id to that table.

This column has a special data type serial, which turns the column into an auto-incrementing number. This means that, whenever you add a new professor to the table, it will automatically get an id that does not exist yet in the table: a perfect primary key!

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Add a new column id with data type serial to the professors table.