2.2. Query Languages and Data Functions

Database operations can be split into those manipulating the database itself (that is, the logical and physical structure of the files comprising the database) and those manipulating the data stored within these files. The former topic is generally database-specific and can be implemented in various ways, but the latter is typically carried out by using a query language.^[2]

^[2] We use the term "query language" very loosely. We stretch it from verb-based command languages, like SQL, all the way down to hard-coded logic written in a programming language like Perl.

All query languages, from the lowest level of using Perl's string and numerical handling functions to a high-level query language such as SQL, implement four main operations with which you can manipulate the data. These operations are: