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One type of field is the link, which connects a given record to associated records. Using links, records link to other records, and to other records, forming a tree. An example is a "customer" record that has links to that customer's "orders", which in turn link to "line_items". The hierarchical database model mandates that each child record ...
On the other hand, non-schema objects may include: [6] users; roles; contexts; directory objects; Schema objects do not have a one-to-one correspondence to physical files on disk that store their information. However, Oracle databases store schema objects logically within a tablespace of the database. The data of each object is physically ...
Cascading can be implemented in terms of chaining by having the methods return the target object (receiver, this, self).However, this requires that the method be implemented this way already – or the original object be wrapped in another object that does this – and that the method not return some other, potentially useful value (or nothing if that would be more appropriate, as in setters).
The terms schema matching and mapping are often used interchangeably for a database process. For this article, we differentiate the two as follows: schema matching is the process of identifying that two objects are semantically related (scope of this article) while mapping refers to the transformations between the objects. For example, in the ...
The DROP statement destroys an existing database, table, index, or view. A DROP statement in SQL removes a component from a relational database management system (RDBMS). The types of objects that can be dropped depends on which RDBMS is being used, but most support the dropping of tables, users, and databases.
A logical data model or logical schema is a data model of a specific problem domain expressed independently of a particular database management product or storage technology (physical data model) but in terms of data structures such as relational tables and columns, object-oriented classes, or XML tags.
A schema crosswalk is a table that shows equivalent elements (or "fields") in more than one database schema. It maps the elements in one schema to the equivalent elements in another. It maps the elements in one schema to the equivalent elements in another.
In the steady state, one version of an application only understands one version of a schema. So the most basic strategy is to shut down the application, execute the schema migration, and then start the newer version of the application. While simple, this strategy causes a downtime. Depending on the criticality of the system and its usage ...