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Outer quantifiers in object-oriented queries and views of database systems
Outer quantifiers in object-oriented queries and views of database systems
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机译:面向对象的查询和数据库系统视图中的外部量词
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摘要
The system, method, and program of this invention provides for a new type of quantifier that is useful for object-oriented queries that reference collections and nested collections of objects. The invention is applicable to any other type of database where the data has a hierarchical relationship, also. This new type of quantifier is called an outer quantifier. The outer quantifier appears in the language of the query (in the FROM clause) and creates a new runtime semantic. The function and semantics provided by outer quantifiers is similar to that provided partly by left outer joins in relational systems. Outer quantifiers are bound to a null instance if the collection over which they are defined is empty. Outer quantifiers are a simple way of expressing queries so that objects having empty collections of nested objects are included in the result, also.
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