Object Query Language (OQL)
OQL is an SQL-like declarative language that provides a rich environment for efficient querying
of database objects, including high-level primitives for object sets and structures. OQL provides
a superset of the SQL-92 SELECT syntax. This means that most SQL SELECT statements which run on
relational DBMSs tables work with the same syntax and semantics on ODMG collection classes.
--参见http://www.odmg.org/standard/standardoverview.htm
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