A relational database is based on the relational model of data, which organizes data into one or more tables of rows and columns, with a unique key for each row. Generally, each entity type described in a database has its own table with the rows representing instances of that type of entity and the columns representing values attributed to that instance. Since each row in a table has its own unique key, rows in a table can be linked to rows in other tables by storing the unique key of the row to which it should be linked.
The most popular of relational databases are Microsoft SQL Server, Oracle Database, MySQL, and IBM DB2. These relational database management systems are generally used in large business scenarios, except for MySQL, which is used to store data for web applications.
Relational vs. Non-Relational Databases
A non-relational database provides a mechanism for storage and retrieval of data that is modeled in means other than the tabular relations used in relational databases.
A major limitation of relational databases is that each item can only have one attribute. For example, each aspect of a customer’s relationship with a company is stored as separate row items in separate tables. All these tables are linked to each other through the use of relations such as primary keys.
Non-relational databases are significantly different from this model. Key-value pairs allow you to store several related items in one “row” of data in the same table. In a non-relational table, each row would contain the customer’s details so all data relating to one customer would be conveniently stored together as one record.
This seems a superior method of storing data, but it has a significant disadvantage: key-value stores, unlike relational databases, cannot enforce relationships between data items. For instance, customer details (name, social security, address, account number, loan processing number, etc.) would all be stored as one data record (instead of being stored in several tables, as in the relational model). The customer’s transactions would also be stored as another single data record.
Relational Databases: What Advantages Do They Have?
The relational model for databases has been imposed, not without reason, in the electronic data processing environment. We summarize below the main strengths of this database model:
Simplicity: the data model that underlies the relational database is more easily implemented and managed than other models. The vast amount of information (customer data, order lists, account movements) that companies want to store in the long term are organized without problems in the structure of tables on which the relational database model is based.
Scarce data redundancy: the normal forms of the relational model set a norm that has the purpose of avoiding duplications. If the rules of normalization are applied consistently, relational systems facilitate data storage free of redundancies, since it is only necessary to edit the data only once, which simplifies especially the internal and technical maintenance of the data.
High data consistency: standardized relational databases allow the storage of data without contradictions, thus contributing to the consistency of the data. Likewise, relational systems present functions with which integrity conditions are defined and controlled automatically. The transactions that compromise the consistency of the data are blocked.
Set-oriented data processing: the relational database system is based on set-oriented processing that subdivides each entity into minimum values. This allows you to connect different entities through the content, as well as perform complex queries such as JOIN.
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