Schema Evolution in SQL-99 and Commercial (Object-)Relational DBMS
نویسنده
چکیده
A database schema denotes the description of the structure and behavior of a database. Straightforwardly, (database) schema evolution refers to changes of the database schema that occur during the lifetime of the corresponding database. It particularly refers to changes of schema elements already stored in the database. The information about a database schema is stored in the schema catalog. Data stored in these catalogs is referred to as meta-data. In this sense, schema evolution could be seen as a change of the content of the schema catalog. In an object-relational database model, such as proposed in SQL-99 [Int99], a database schema, among others, consists of the following elements:
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