摘要 |
Query objects facilitate accessing data contained in a database by allowing a user to query the database without having to know SQL or the relationships between the underlying tables in the database. These query objects are built from clauses and are related to each other by clause operators. These query operators define operations on the query objects, such as union, intersection, and intersection-complement operators. New query objects are constructed based on operand query objects and the query operators by which the operand query objects are related.
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