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How databases are ran and how SQL works
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Leading Database Products
Product | Sponsor | Type | License | DB-Engines rank |
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Oracle Database | Oracle | Relational | Commercial | 1 |
MySQL | Oracle | Relational | Open source | 2 |
SQL Server | Microsoft | Relational | Commercial | 3 |
PostgreSQL | PostgreSQL Global Development Group | Relational | Open source | 4 |
MongoDB | MongoDB | NoSQL | Open source | 5 |
Database Model
is a conceptual framework for database systems, with three parts:
Data structures that prescribe how data is organized.
Operations that manipulate data structures.
Rules that govern valid data.
Relational Model
A database model based on a tabular data structure. The model was published in 1970 by E. F. Codd of IBM and released in commercial products around 1980. The data structure, operations, and rules are standardized in SQL, the universal query language of relational databases. Relational databases were initially designed for transactional data, such as bank transactions and airline reservations. The rise of the internet in the 1990s generated big data, characterized by unprecedented data volumes and rapidly changing data structures. Many alternative database models and systems, optimized for big data, have appeared since 2000. However, relational databases have gradually improved support for big data and continue to dominate the commercial database market.
Example Database Models
Primary data structure | Initial product releases | Example database system | Strengths | |
---|---|---|---|---|
Hierarchical | Tree | 1960s | IMS | Fast queries |
Network | Linked list | 1970s | IDMS | Fast queries |
Relational | Table | 1980s | Oracle Database | Productivity and simplicity |
Object | Class | 1990s | ObjectStore | Integration with object-oriented programming languages |
Graph | Vertex and edge | 2000s | Neo4j | Flexible schema |
Document | XML | 2010s | MongoDB | Flexible schema |
Data Structure Terms
Databases | Mathematics | Files |
---|---|---|
Table | Relation | File |
Column | Attribute | Field |
Row | Tuple | Record |
Data type | Domain | Data type |