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Lab Experiment 2: Database Table creation, Maintenance & Views 2.3: Preparation (1) The primary key of a table is a column (or combination of columns in a table) that are used to uniquely identify rows in a table. This means that two different rows in a table may never have the same value in their primary key, and for every row in the table the primary key must have a value. Therefore, if the primary key column(s) are declared NULL, two or more rows in the primary key can have identical values and thus they will NOT be unique. Also the definition of the primary key states that a primary key must have a value and by declaring it NULL, the user has an option of leaving it empty, which is violating the primary key's rules. The primary key column(s) must be declared NOT NULL, to maintain the integrity of data which is entered in...

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