Abstract
A group select operation has been defined for relational algebra.
This operation is found to be useful for very efficiently reducing
expressions of non procedural relational languages that permit
natural quantifiers. Conceptually, the operation first partitions a
relation into blocks of tuples that have the same value for an attribute
or attribute concatenation. It then extracts each block for which a
specified number of tuples meet a specified condition. The quantity
of tuples for the operation is specified by means of a natural
quantifier. Performance of the group-select operation
will be poor with conventional file processing, making the operation more
suitable for use with data base machine with an associative memory.
Notes
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