Summary

The design of a database management system is affected by the CAP theorem. Relational databases and NoSQL databases are not rivals but complementary. One can utilize different database categories in a single software application. In certain scenarios, one can use the key-value store as a cache engine on top of the relational database to gain performance.

Relational and object-relational databases are the market-dominant databases. Relational databases are based on the concept of relation, and have a very robust mathematical model. Object-relational databases such as PostgreSQL overcome the limitations of relational databases by introducing complex data types, inheritance, and rich extensions.

Relational databases are based on the relation, tuple, and the attribute concepts. They ensure data validity and consistency by employing several techniques such as entity integrity, constraints, referential integrity, and data normalization.

Modern RDBMS can capture semantic constraints by using SQL procedural languages, triggers, and rule systems. PostgreSQL can support several procedural languages including C, PL/pgSQL, PL/Python, and so on.

Relational algebra enables the developer to rewrite the SQL code in alternative ways. It also enables the RDBMS to generate, compare, and choose an execution plan from different execution plans. Relational algebra provides a closed set of operations which can be combined together to answer complex queries.

SQL is the standard relational database language. SQL standards are maintained by ISO, and SQL code is often compatible with different relational databases.

Data modeling is very important for communicating business requirements; it can help in achieving the concept of separation of concerns. There are several data modeling perspectives, namely, conceptual, logical, and physical perspectives.

In the next chapter, an overview of PostgreSQL will be introduced. The next chapter will discuss the advantages, history, capabilities, and forks of PostgreSQL. It also will show how one can install PostgreSQL on different platforms including Linux and Windows.