2. Relational Algebra
When we use SQL to manipulate data in a database, we are actually using something known as the relational calculus, a method for using a single command to instruct the DBMS to perform one or more actions. The DBMS must then break down the SQL command into a set of operations that it can perform one after the other to produce the requested result. These single operations are taken from the relational algebra.
Note: Don't panic. Although both the relational calculus and the relational algebra can be expressed in the notation of formal logic, there is no need for us to do so. You won't see anything remotely like mathematic notation in this chapter.
In this chapter we will look at seven relational algebra operations. The first ...
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