Post by account_disabled on Feb 20, 2024 4:08:42 GMT -8
We already know, from what has been published on previous occasions, that the relational model in database management is currently the most used model in the management of dynamic data (or in other words, data subject to modifications and updates). . However, relational database management involves a thick web of concepts that can sometimes be somewhat difficult for laymen to handle. Today we propose to prepare a brief glossary of terms with the most important concepts in this area and how they come into play in the management of relational databases. Basic concepts of the relational model Relational model : database organization and management model consisting of storing data in tables composed of rows, or tuples , and columns or fields.
It is distinguished from other models, such as the hierarchical one, by being more understandable for the inexperienced user, and by being based on predicate logic to establish relationships between different data. It arises as a solution to the growing variety of data that makes up data warehouses and we can summarize the concept as a USA Student Phone Number List collection of tables (relationships). relational model in database management Table : is the name given to each of the relationships established between the stored data; each new relationship gives rise to a table. They are made up of rows , also called tuples, where the elements that configure the table are described (that is, the elements of the relationship established by the table), columns or fields, with the corresponding attributes and values, and the domain , a concept that groups all the values that can appear in each column. Keys : elements that prevent duplicate records, one of the great disadvantages of other database organization and management models.
There are two main types of keys: primary keys and secondary or foreign keys. Primary keys : These are the attributes (columns) according to the type of relationship that has been defined in the table. Other specific and own attributes can be added. Foreign or secondary keys : These are the keys that are defined for each of the primary keys established for the elements or entities of a relationship. Identity constraint : limits and restrictions imposed on relationships, essential to maintain the correct meaning of the database. It is a concept closely linked to the integrity rules of the relational model, compliance with which is guaranteed by the primary and foreign keys. There are 4 basic types of integrity constraints : the required data (fields or columns must always have an attribute or a value) the validity check (tables must contain only the data corresponding to the corresponding relationship defined by each table) entity and referential integrity ( the former ensure that the primary keys have a unique value for each tuple, and the latter ensure that the primary and foreign keys maintain their integrity) Integrity rules : rules that guarantee data integrity , that is, the plausible correspondence of data with reality.