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Database Consistency and Its Role Within Transactions

Consistency ensures that the structures of a database are logical

By Mike Chapple Mike Chapple Writer University of Idaho Auburn University Notre Dame Former Lifewire writer Mike Chapple is an IT professional with more than 10 years' experience cybersecurity and extensive knowledge of SQL and database management. lifewire's editorial guidelines Updated on April 9, 2020 Tweet Share Email Maciej Frolow / Getty Images Tweet Share Email MS Office Word Excel Powerpoint Outlook Database consistency states that only valid data will be written to the database. If a transaction is executed that violates the database's consistency rules, the entire transaction will be rolled back and the database will be restored to its original state. On the other hand, if a transaction successfully executes, it will take the database from one state that is consistent with the rules to another state that is also consistent with the rules. Database consistency doesn't mean that the transaction is correct, only that the transaction didn't break the rules defined by the program. Database consistency is important because it regulates the data that is coming in and rejects the data that doesn't fit into the rules. Consistency rules are often enforced through constraints at a field level. A constraint specifies a rule governing a given record or field-level value.

Example of Consistency Rules at Work

For example, a column in a database may only have the values for a coin flip as "heads" or "tails." If a user were to attempt to put in "sideways," consistency rules for the database would not allow it. You may have experience with consistency rules about leaving a field on a web page form empty. When a person is filling out a form online and forgets to fill in one of the required spaces, a NULL value goes to the database, causing the form to be rejected until the blank space has something in it. Consistency is the second stage of the ACID model (Atomicity, Consistency, Isolation, Durability), which is a set of guidelines for ensuring the accuracy of database transactions. The ACID Database Model Was this page helpful? Thanks for letting us know! Get the Latest Tech News Delivered Every Day Subscribe Tell us why! Other Not enough details Hard to understand Submit More from Lifewire The ACID Database Model An Introduction to Databases for Beginners The Basics of Database Normalization Net Neutrality Explained Glossary of Common Database Terms How to Export Data to Excel BASE Model of Database Development How to Whitelist a Domain in Mac OS X Mail App What Is the Definition of a Database Query? Use Access Input Forms to Enter and Modify Data Understanding the Isolation Property in a Database Are Self-Driving Cars Legal in Your State? What Is Web3? Full Functional Dependency in Database Normalization What Is mysqldump and How Do I Use It? What Are Biometrics? Newsletter Sign Up Newsletter Sign Up Newsletter Sign Up Newsletter Sign Up Newsletter Sign Up By clicking “Accept All Cookies”, you agree to the storing of cookies on your device to enhance site navigation, analyze site usage, and assist in our marketing efforts. Cookies Settings Accept All Cookies