How do relational databases work?
In: Technology
Lets give it a try: A relational DB is a way for storing and accessing data. It is based on “relational algebra”.
Most commonly, a data model is designed first, then data is deconstructed by the process of “normalization”. This aims to turn your data in a basic form like into separate tables. E.g. one table for customers and one for orders.
The so called “keys” are important so you can “join” the data again and make a report that answers questions like “what did each customer order?”. One benefit comes from you not needing to store all those “answers” and reports permanently, but rather modify your “query”.
So why not put it in a single table then you ask? Because the normalized data is more flexible and eliminates waste like storing same data multiple times. It’s one of the key features of RDBMS, which was invented around the 70’s where hardware was very limited.
The language to query the data is called SQL; there are variations to this like T-SQL or PL/SQL. An RDBMS is the system/software you choose e.g. SQL Server or Oracle.
So taking the example, when an RDBMS contains the pure facts about customers and orders, it can say “ask me anything about the customers and orders and i can answer them for you”. This can include something basic like “how many customers do we have?” to more complex ones like “what is the most ordered item and by which customer?”
Source: I’m a DBA and developer.
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