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A candidate key, or simply a key, of a relational database is any set of columns that have a unique combination of values in each row, with the additional constraint that removing any column could produce duplicate combinations of values. A candidate key is a minimal superkey, [1] i.e., a superkey that does not contain a smaller one. Therefore ...
An optional header record (there is no sure way to detect whether it is present, so care is required when importing). Each record should contain the same number of comma-separated fields. Any field may be quoted (with double quotes). Fields containing a line-break, double-quote or commas should be quoted. (If they are not, the file will likely ...
In the relational model of databases, a primary key is a designated attribute that can reliably identify and distinguish between each individual record in a table.The database creator can choose an existing unique attribute or combination of attributes from the table (a natural key) to act as its primary key, or create a new attribute containing a unique ID that exists solely for this purpose ...