October 2002
Beginner
864 pages
18h 41m
English
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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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