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Reviewer: Jaroslav Pokorny

The book attempts to present an overview of the current state of the art of database technology, that is, mainly data models, database languages, and database architectures, including approaches to ensuring data consistency. Separate chapters are devoted to postrelational and NoSQL databases. Unfortunately, its approach is very unsystematic: some important topics are presented in great detail, some in less, and some not at all. Chapter 1 provides a very informal introduction to the relational data model, structured query language (SQL), big data, and NoSQL databases. Rather unusually, graph databases and the Cypher query language are briefly presented in the last category. Chapter 2 is devoted to data modeling, particularly to the entity-relational (ER) model, relational data model, and graph model, with some rules for implementing the ER schema in relational and graph environments. Unfortunately, a lot of not-too-relevant notions from graph theory are presented here. On the other hand, a conceptual schema is not defined at all; instead, the ER model is used. Chapter 3 describes relational algebra and SQL. While relational algebra is described in detail, only basic language options for SQL are provided. The query by example (QBE) language and some constructs of Cypher are covered, along with short sections about NULL values, integrity constraints, and so on. Chapter 4, "Ensuring Data Consistency," discusses parallel processing in centralized and distributed database management system (DBMS) architectures. Transaction processing, including its ACID and BASE properties, is described in sufficient detail. Chapter 5 discusses some details of a DBMS architecture. The reader finally learns more about the SQL database schema here. In this context, semistructured and unstructured data are recommended for database storage and processing. The chapter includes short sections devoted to data indexing, query optimization, and parallel processing with MapReduce. Finally, it presents the well-known five-layer model for relational databases and various storage structures. Chapter 6 is "Postrelational Databases"; clearly, object-relational and temporal databases belong here, but federated databases belong in chapter 5. The last chapter (7) is so short that it is surprising its title ("NoSQL databases") appears in the title of the entire book. In conclusion, the book can be recommended to anybody who needs a basic overview of databases, unfortunately with some not-too-important details, for example, fifth normal form (5NF) and Voronoi diagrams. This unbalanced approach reduces the quality of the book.