Exploring Types of Constraints

Now, you'll study the different types of constraints that can be created on database tables. Following is a list of those constraints:

  • NOT NULL

  • Primary key

  • Unique

  • Foreign key

  • Check

Each of these constraints have their own function. The functions and syntax of each of these constraints are discussed in the following subsections, as well as their place in a relational database.

NOT NULL Constraints

When you initially create a table, you must assign a data type to each column in the table. The data type assigned to a column tells the database what kind of data can be inserted into that column in a table. The different types of data mainly include Character data, Numeric data, and Date and Time data.

A basic CREATE TABLE ...

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