Various Types of Database
- Hierarchical Database: Store data in hierarchical structure such as folder and files.
- Relational Database: Store table type data with columns and rows. Devised based on relational algebra.
- Object Oriented Database: Store object itself as a data.
- XML Database: Store XML-form data. XML is a data type using tags such as ‘<data>data<\/data>’.
- Key-Value Store (KVS): Store data in key-value pair.
SQL is only available in Relational Database.
RDBMS is used in various systems. Most main frames use RDBMS. RDBMS is also used in Internet, smartphones.
Database Products
There are many RDBMS products.
- Oracle: The most widely used.
- DB2
- SQL Server
- PostgreSQL: Open sourse.
- MySQL: Open sourse.
- SQLite
Standard SQL and Dialect SQL
As there are variety of RDBMS products and each of them provides unique functions, SQL which is slightly different from standard one has developed.
The most well-known examples of dialect are keyword omission(e.g. ‘FROM’ keyword behind ‘DELETE’) and ‘join’.
However, using standardized SQL is recommended.
All images, except those with separate source indications, are excerpted from lecture materials.
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