Relational algebra is a simple and consistent query language that is often used to explain principles of relational operations. While many books and articles deal with the theory of relational algebra, its practical applicability is generally neglected. Moreover, there is no software support for evaluating relational algebra expressions: contemporary relational database management systems implement only the SQL query language. Finally, the common syntax for relational algebra is based on Greek alphabet, making queries difficult to type on standard keyboards. We divide this work into two parts, theoretical and practical. In the theoretical part you will find definitions of relational algebra operations accompanied by clear examples. The practical part proposes new and approachable ASCII-compatible syntax for relational algebra. Furthermore, it explores the possibilities of automated translation of queries into SQL. A tool for checking syntactic and semantic correctness is described in detail. This book is among the few resources dealing with direct practical applications of relational algebra. Moreover, it is a great starting point for everyone interested in the background theory.
