If you work with data, sooner or later, you will come into contact with databases. This chapter introduces various databases (relational and NoSQL) and related APIs. A relational database is a database that has a collection of tables containing data organized by the relations between data items. A relationship can be set up between each row in the table and a row in another table. A relational database does not just pertain to relationships between tables; firstly, it has to do with the relationship between columns inside a table (obviously, columns within a table have to be related, for instance, a name column and an address column in a customer table); secondly, it relates to connections between tables.

NoSQL (Not Only SQL) databases are undergoing substantial growth in Big Data and web applications. NoSQL systems may in fact permit SQL-like query languages to be employed. The main theme of NoSQL databases is allowing data to be stored in a more flexible...