Database language extended to accommodate entity-relationship models

摘要

Embodiments extend the relational model and language of standard SQL, to recognize features of higher level entity-relationship models (ERMs). SQL extensions implemented in the data design language (DDL) incorporate Entities (and Views) having custom-defined/semantic structure, rather than being limited to primitive types (e.g. flat tables as in standard SQL). Entities are defined similar to structured types with an underlying persistency, but with a uniquely identifying leading key. In DDL, these entities are combined with associations in the data model. The associations of the extended SQL reflect relationships between entities in the ERM. Associations are specified by adding an element to a source entity, with an association type pointing to a target entity. This may be complemented by providing optional information (e.g., cardinality, keys, filter conditions), up to a complete JOIN condition. In the query language (QL), JOINs may be replaced by the use of simple path expressions.

主权项

1. A computer-implemented method comprising:
providing a database organized according to a relational model; providing a database engine in communication with the database through a language describing the relational model; providing an application comprising an entity-relationship model (ERM), the ERM including a first entity, a second entity, and a relationship between the first entity and the second entity; and causing a query engine of the application to communicate a query to the database engine utilizing a language extension comprising,
a first structured entity type including a first key and indicating the first entity,a second structured entity type including a second key and indicating the second entity, anda structured association type reflecting the relationship and including a first parameter clause specifying cardinality information, and including a second parameter clause specifying a combination of alternative key elements in a nested structure comprising an alias name of one alternative key element in a substructure of the second structured entity; and causing the database engine to return a query result to the query engine based upon the language extension.