The reverse star schema is a
schema
The word schema comes from the Greek word ('), which means ''shape'', or more generally, ''plan''. The plural is ('). In English, both ''schemas'' and ''schemata'' are used as plural forms.
Schema may refer to:
Science and technology
* SCHEMA ...
optimized for fast
retrieval
Retrieval could refer to:
Computer science
* RETRIEVE, Tymshare database that inspired dBASE and others
* Data retrieval
* Document retrieval
* Image retrieval
* Information retrieval
* Knowledge retrieval
* Medical retrieval
* Music informati ...
of large quantities of descriptive
data
In the pursuit of knowledge, data (; ) is a collection of discrete values that convey information, describing quantity, quality, fact, statistics, other basic units of meaning, or simply sequences of symbols that may be further interpret ...
. The design was derived from a warehouse
star schema,
and its adaptation for descriptive data required that certain key characteristics of the classic star schema be "reversed".
Model
The relation of the central table to those in
dimension tables is one-to-many, or in some cases many-to-many rather than many-to-one; the primary keys of the central table are the
foreign key A foreign key is a set of attributes in a table that refers to the primary key of another table. The foreign key links these two tables. Another way to put it: In the context of relational databases, a foreign key is a set of attributes subject to ...
s in dimension tables, and the main tables are, in general, smaller than the dimension tables.
Main table columns are typically the source of
query constraints, as opposed to dimension tables in the classical star schema. By starting queries with the smaller table, many results are filtered out early in the querying process, thereby streamlining the entire
search path.
To add further flexibility, more than one main table is allowed, with main and submain tables having a one-to-many relation. Each main table can have its own dimension tables. To provide further
query optimization, a data set can be partitioned into separate physical schemas on either the same
database server or different database servers.
See also
*
Snowflake schema
References
{{DEFAULTSORT:Reverse star schema
Data warehousing
Data modeling