发明授权
US5797136A Optional quantifiers in relational and object-oriented views of database
systems
失效
数据库系统的关系和面向对象视图中的可选量词
- 专利标题: Optional quantifiers in relational and object-oriented views of database systems
- 专利标题(中): 数据库系统的关系和面向对象视图中的可选量词
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申请号: US539561申请日: 1995-10-05
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公开(公告)号: US5797136A公开(公告)日: 1998-08-18
- 发明人: Philip L. Boyer , Gerald G. Kiernan
- 申请人: Philip L. Boyer , Gerald G. Kiernan
- 申请人地址: NY Armonk
- 专利权人: International Business Machines Corporation
- 当前专利权人: International Business Machines Corporation
- 当前专利权人地址: NY Armonk
- 主分类号: G06F17/30
- IPC分类号: G06F17/30
摘要:
A system, method, and program enables database management systems for relational and object-oriented databases to recognize a quantifier in a query as being designated as optional. An optional quantifier will participate in a query depending upon certain conditions. If the columns (or objects) projected out in the view that are dependent upon the quantifier are not used by the query, the quantifier is dropped from the definition of the view. The query is processed using only the relations in the view not associated with the optional quantifier. The results returned are as if a left outer join operation with duplicate elimination had been performed, although the actual processing of the query was independent of, i.e., did not involve, a left outer join operation. If the columns (or objects) projected out in the view that are dependent upon the quantifier are used by the query, the optional quantifier remains in the definition of the view and the query is processed using a join operation.
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