3. SQL¶
In this chapter we describe the process of concieving, creating and querying a database.
3.1. The MERISE method¶
MERISE is an Information System Design and Development methodology widely used in France. The framework of MERISE has three cycles: abstraction cycle, approval cycle and life cycle. The abstraction cycle uses the three database levels (conceptual, logical and physical). The approval cycle recognizes the necessity of identifying decision points during the development of the information system. The life cycle consists of (long range) planning, initial study, detailed study, implementation, launching and maintenance.
Adopting the Mersie methodology allows in a first step to identify the reality of the subject at hand. This means defining the type of data to be used, organinsing the metadata i.e. the information relevant to the data and eliminating redondances. In this section we detail the different levels of the abstraction cycle. The goal is to get a model that organises the data in interconnecting tables in a way to avoid redondances and such that anyone can find their way through the data. The first step is to make a census of the data.