| 摘要 |
An object oriented query such as an enterprise java bean query is translated into a corresponding relational query by identifying an inter-hierarchal relationship relating two or more object oriented hierarchies; identifying a source object oriented hierarchy of the inter-hierarchal relationship; mapping the source object oriented hierarchy into corresponding source relational tables; building a source series of joins between the source relational tables, the source series being ordered in a top-down order from a root of the source object oriented hierarchy; identifying a target class of the inter-hierarchal relationship; mapping the target object oriented hierarchy into corresponding target relational tables; building a target series of joins between the target relational tables, the target series comprising a first target series and a second target series, the first target series corresponding to the target class, a root of the target object oriented hierarchy, and intervening nodes between the target class and the root of the target object oriented hierarchy, and the second target series corresponding to nodes in leaves of the target object oriented hierarchy located below the target class; and combining the source series of joins and the target series of joins into the corresponding relational query. For a query selection based upon a plurality of relationships between the object oriented hierarchies, the steps may be repeated for each of the plurality of relationships. The combined series of joins may be further reordered by recursively finding a join relationship between a current node and a preceding node in the combined series of joins. To improve performance, a join above a target of a relationship is built as an inner join, and a join below the target of relationship is built as an outer join.
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