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Data domain refers to the acceptable values for a specific field in a database. It ensures consistency and prevents meaningless results. A programmer defines the data domain using a lookup table and reference table to validate entries.
“Data domain” is a term used in database fields and data management. It refers to the range of acceptable values that a particular row or field can contain. Enforcement of data domains keeps information in a database consistent and within acceptable parameters, avoiding situations where databases produce meaningless results or are unable to answer specific queries due to lack of sufficient information. Defining a data domain is done by a database programmer, who often establishes a list of appropriate values for an input field in the program.
Perhaps the easiest way to understand the concept of a data domain is to look at an example. Consider a field in an employee database where an end user is supposed to record the employment status of individual employees. Each employee of the organization will be a current or past employee; therefore, these are the only acceptable entries in the data domain for that field. When creating the database, the programmer typically indicates that these are the only acceptable responses for someone entering data into the “Employee State”.
Another, more complex example of a data domain would be a field for an employee’s phone number. In the United States, the data domain in this field should be limited to numbers only, with a maximum length of 10 characters; in other words, an area code plus a seven-digit phone number. A programmer wishing to impose an even tighter level of control over the data domain could program it so that only actual area codes and area codes can be used, preventing people from attempting to claim (999) 999-9999 as a phone number. In both examples, the limits placed on the actual data domains are achieved using a tool known as a lookup table.
Acceptable data values are typically stored in what is known as a reference table. A reference table is a database-linked table that contains acceptable values or ranges of values for data for specific tables in the database. Information entered into the database is compared to the referenced table to determine if the user accidentally entered an invalid entry. Invalid entries are usually marked with an error message and require a second chance to enter a correct value into the database.
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