4.5 Relational Data Manipulation Languages (DMLs)
There are a variety of languages, called relational data manipulation languages (DMLs) used by relational database management systems to manipulate and/or modify data in the database.
4.5.1 Categories of DMLs
Some DMLs are procedural or proscriptive, meaning the user tells the system exactly how to manipulate the data. Relational algebra is an example of a procedural language that we will discuss. Others are nonprocedural or declarative, which means the user states what data is needed but not exactly how it is to be located. Relational calculus and SQL are nonprocedural languages. Some languages are graphical, allowing the user to give an example or illustration of what data should be found. ...
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