Search results
Results From The WOW.Com Content Network
SQLAlchemy offers tools for database schema generation, querying, and object-relational mapping. Key features include: A comprehensive embedded domain-specific language for SQL in Python called "SQLAlchemy Core" that provides means to construct and execute SQL queries. A powerful ORM that allows the mapping of Python classes to database tables.
A database abstraction layer (DBAL [1] or DAL) is an application programming interface which unifies the communication between a computer application and databases such as SQL Server, IBM Db2, MySQL, PostgreSQL, Oracle or SQLite. Traditionally, all database vendors provide their own interface that is tailored to their products.
The standard relational algebra and relational calculus, and the SQL operations based on them, are unable to express directly all desirable operations on hierarchies. The nested set model is a solution to that problem. An alternative solution is the expression of the hierarchy as a parent-child relation. Joe Celko called this the adjacency list ...
Object–relational mapping (ORM, O/RM, and O/R mapping tool) in computer science is a programming technique for converting data between a relational database and the memory (usually the heap) of an object-oriented programming language. This creates, in effect, a virtual object database that can be used from within the programming language.
A model of this "theory" closely corresponds to a database, which can be seen at any instant of time as a mathematical object. Thus a schema can contain formulas representing integrity constraints specifically for an application and the constraints specifically for a type of database, all expressed in the same database language. [1]
A graph database is a database that is based on graph theory. It consists of a set of objects, which can be a node or an edge. It consists of a set of objects, which can be a node or an edge. Nodes represent entities or instances such as people, businesses, accounts, or any other item to be tracked.
So, for example, instead of making a query into a database to fetch all users from several tables, the application can call a single method from a DAL which abstracts those database calls. Applications using a data access layer can be either database server dependent or independent.
The HMI/SCADA Module Layer contains mainstay products of the Ignition Platform. Vision is the main visualization module, SQL Bridge is a bidirectional OPC to SQL database historian and transaction manager, Reporting generates dynamic Pdf reports, and Mobile allows access to HTML 5 compatible devices such as iPads, iPods, Android, Smartphone ...