May 2020
Beginner
564 pages
14h 9m
English
Content preview from Learn SQL Database Programming
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Domain integrity
To ensure that data values follow defined rules for formatting, range, and value using check and default constraints, you use domain integrity.
The check constraint is used to ensure that all values in a column are within a range of values. This type of key can be applied to any data type and is used to ensure that values aren't invalid. A check constraint is enforced with user-defined conditions and evaluates as either true or false. You can define a check constraint on a single column or a combination of columns in a table.
Since null doesn't evaluate as false, it can be inserted or updated into a field with a check constraint. So, because null evaluates to unknown, it can bypass a check constraint. If you want the column ...
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