PostGIS: Extension of Postgres that allows the entry of geographical data.
Geographical data: data that are linked to a geometry, that is an object describing how to represents and in which projection the data.
Database: An SQL database is an organized collection of data into tables so that it can be easily accessed. In QBuildings, there is one database per area of interest.
Schema: A schema holds all objects in PostgreSQL (except for roles and tablespaces). It acts as a namespace within a database. It is the first subdivision of a database.
Tables: Tables are the entities within a db within a schema where data are stored and organised in columns.
Columns: Columns are the fields of tables. They have a name, a type of data (int, object, geometry, …) and some options, mainly:
Primary key column: The column (or columns) that will serve as a unique identifier for each row of the table. Which means each row can be retrieved by knowing this unique attribute.
Foreign key column: If a table is related to another one (for instance table roofs is related to buildings as each roofs belongs to a buildings), this column ensure that the identifier exists in the related table. Usually, a foreign key is link to the primary key of the related table.