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An OLTP system is an accessible data processing system in today's enterprises. Some examples of OLTP systems include order entry, retail sales, and financial transaction systems. [5] Online transaction processing systems increasingly require support for transactions that span a network and may include more than one company.
CRUD functionality can for example be implemented with document databases, object databases, XML databases, text files, or binary files. Some big data systems do not implement UPDATE, but have only a timestamped INSERT (journaling), storing a completely new version of the object each time.
A database model is a type of data model that determines the logical structure of a database and fundamentally determines in which manner data can be stored, organized, and manipulated. The most popular example of a database model is the relational model (or the SQL approximation of relational), which uses a table-based format.
SQL includes operators and functions for calculating values on stored values. SQL allows the use of expressions in the select list to project data, as in the following example, which returns a list of books that cost more than 100.00 with an additional sales_tax column containing a sales tax figure calculated at 6% of the price.
Database transactions where a transaction atomically includes perhaps a write, a read and a matching delete operation. Taking a "snapshot" of the database before running any tests and rolling back to the snapshot after each test run. This may be automated using a framework such as Ant or NAnt or a continuous integration system such as ...
support for hooks (methods which can validate or modify database input and output) and event listeners to structure business-related logic; column aggregation inheritance (similar objects can be stored in one database table, with one type-column specifying the subtype of the particular object - the correct subclass is always returned when a ...
For example, transaction A may access portion X of the database, and transaction B may access portion Y of the database. If at that point, transaction A then tries to access portion Y of the database while transaction B tries to access portion X, a deadlock occurs, and neither transaction can move forward. Transaction-processing systems are ...
For example, to undo a delete selection command, the object may contain a copy of the deleted text so that it can be re-inserted, if the delete selection command must be undone. Note that using a separate object for each invocation of a command is also an example of the chain of responsibility pattern. The term execute is also ambiguous.