Search results
Results from the WOW.Com Content Network
The database schema is the structure of a database described in a formal language supported typically by a relational database management system (RDBMS). The term " schema " refers to the organization of data as a blueprint of how the database is constructed (divided into database tables in the case of relational databases ).
The primary key is a column, or a set of columns, that is used to uniquely identify each row. An example might be Product ID or Order ID. Set up the table relationships – Look at each table and decide how the data in one table is related to the data in other tables. Add fields to tables or create new tables to clarify the relationships, as ...
G-CORE is a composable language which is closed over graphs: graph inputs are processed to create a graph output, using graph projections and graph set operations to construct the new graph. G-CORE queries are pure functions over graphs, having no side effects, which mean that the language does not define operations which mutate (update or ...
Main page; Contents; Current events; Random article; About Wikipedia; Contact us; Help; Learn to edit; Community portal; Recent changes; Upload file
In the context of SQL, data definition or data description language (DDL) is a syntax for creating and modifying database objects such as tables, indices, and users. DDL statements are similar to a computer programming language for defining data structures, especially database schemas. Common examples of DDL statements include CREATE, ALTER ...
There is only one conceptual schema per database. Uniface implements the conceptual schema as the Application Model (in various Uniface versions known as the Business Object Model and the Application Object Model). External schema—different external (user) views of the data. There can be many external schemas for a database.
A schema is a model, usually depicted by a diagram and sometimes accompanied by a language description. The three schemas used in this approach are: [5] External schema for user views; Conceptual schema integrates external schemata; Internal schema that defines physical storage structures.
Prepare the schema so that it can hold data in both the old and new formats. This might mean adding a new version of a column or a table, without affecting existing data. Deploy a new version of the application which writes data in both the old and new formats (hence the name dual writing). It's important to ensure consistency of these writes ...