Database Glossary – Q
Useful Terms For Working With Data

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Q

QBE

Query-By-Example, a tabular language for expressing queries, in which sketching an abbreviated ‘schema’ of the output specifies a query desired, along with any criteria that should be applied to the fields desired.

Query

1) Literally, a question you ask about data in the database in the form of a command written in a query language, defining sort order and selection, that is used to generate an ad hoc list of records.

2) The output subset of data produced in response to a query.

Query Language

See: Language, Query.

Query Resolution

The process of collecting the data needed to answer a query.

Query, Ad hoc

A temporary query for which neither the criteria nor resulting output are saved.

Query, Base

Same as a ground query.

Query, Ground

A query in which all of the fields are taken directly from tables; none are taken from
the output of other queries.

Query, Nested

A statement that contains one or more sub queries.

Query, Persistent

A query that is stored for reuse.

Query, Recursive

A query from which output is then used as input for the same query.

Query, Sub

A query contained within another query, usually hierarchically larger in scope.

Query, Unsafe

A query in which the output is possibly infinite. This most often occurs in queries which are recursive or which contain negation. Such queries are disallowed by many database management systems to prevent unsafe queries.

Query-By-Example

See: QBE.