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diff --git a/blog/content/notes/tech/about-relational-databases.gmi b/blog/content/notes/tech/about-relational-databases.gmi new file mode 100644 index 00000000..c66a530f --- /dev/null +++ b/blog/content/notes/tech/about-relational-databases.gmi @@ -0,0 +1,27 @@ +# About relational databases + +## What is a relation? + +A common misconception is that the "relations" in a relational database are about relations between database tables. + +Actually, the relations in a relational database are the tables. + +A relation "relates" a set of values with another set of values. + +For example, a relation can relate the name of a person with their birth date and birth place. For example: + +(person name) => (birth date, birth place) +(Alice) => (1979-12-03, Barcelona) +(Bob) => (1995-03-04, Paris) +... + +Many computer languages have similar concepts: + +* Python mapping types such as dict +* C++ std::map +* Java java.util.Map +* C# System.Collections.Generic.Dictionary +* Javascript Object +* PHP arrays + +Relations are a natural concept, so although non-relational data systems exist, most data can be stored as relations. |