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VOOZH | about |
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VOOZH | about |
By Mark Drake
Manager, Developer Education
When designing an SQL database, there may be cases where you want to impose restrictions on what data can be added to certain columns in a table. SQL makes this possible through the use of constraints. After applying a constraint to a column or table, any attempts to add data to the column or table that doesn’t align with the constraint will fail.
Different SQL implementations have their own unique ways of dealing with constraints. This guide provides an overview of the syntax that many database management systems use to manage constraints, using MySQL in examples throughout.
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Structured Query Language — commonly known as SQL — is a language used to define, control, manipulate, and query data held in a relational database. SQL has been widely adopted since it was first developed in the 1970s, and today it’s the predominant language used to manage relational database management systems.
Ideal for managing structured data (data that can fit neatly into an existing data model), SQL is an essential tool for developers and system administrators in a wide variety of contexts. Also, because of its maturity and prevalence, candidates with SQL experience are highly sought after for jobs across a number of industries.
This series is intended to help you get started with using SQL. It includes a mix of conceptual articles and tutorials which provide introductions to various SQL concepts and practices. You can also use the entries in this series for reference while you continue to hone your skills with SQL.
Note: Please be aware that the tutorials in this series use MySQL in examples, but many RDBMSs use their own unique implementations of SQL. Although the commands outlined in this tutorial will work on most RDBMSs, the exact syntax or output may differ if you test them on a system other than MySQL.
Browse Series: 27 tutorials
Former Technical Writer at DigitalOcean. Focused on SysAdmin topics including Debian 11, Ubuntu 22.04, Ubuntu 20.04, Databases, SQL and PostgreSQL.
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