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In computing, a snowflake schema or snowflake model is a logical arrangement of tables in a multidimensional database such that the entity relationship diagram resembles a snowflake shape. The snowflake schema is represented by centralized fact tables which are connected to multiple dimensions. "Snowflaking" is a method of normalizing the ...
In computing, the star schema or star model is the simplest style of data mart schema and is the approach most widely used to develop data warehouses and dimensional data marts. [1] The star schema consists of one or more fact tables referencing any number of dimension tables. The star schema is an important special case of the snowflake schema ...
An inner join (or join) requires each row in the two joined tables to have matching column values, and is a commonly used join operation in applications but should not be assumed to be the best choice in all situations. Inner join creates a new result table by combining column values of two tables (A and B) based upon the join-predicate.
In this type of join, two relations are connected by their common attributes. MySQL's approximation of a natural join is the Inner join operator. In SQL, an INNER JOIN prevents a cartesian product from occurring when there are two tables in a query. For each table added to a SQL Query, one additional INNER JOIN is added to prevent a cartesian ...
Hash join. The hash join is an example of a join algorithm and is used in the implementation of a relational database management system. All variants of hash join algorithms involve building hash tables from the tuples of one or both of the joined relations, and subsequently probing those tables so that only tuples with the same hash code need ...
Online analytical processing. In computing, online analytical processing, or OLAP (/ ˈoʊlæp /), is an approach to quickly answer multi-dimensional analytical (MDA) queries. [1] The term OLAP was created as a slight modification of the traditional database term online transaction processing (OLTP). [2] OLAP is part of the broader category of ...
Single data (fact) table surrounded by multiple descriptive (dimension) tables Developers often don't normalize dimensions due to several reasons: [5] Normalization makes the data structure more complex; Performance can be slower, due to the many joins between tables; The space savings are minimal; Bitmap indexes can't be used; Query performance.
Join dependency. In database theory, a join dependency is a constraint on the set of legal relations over a database scheme. A table is subject to a join dependency if can always be recreated by joining multiple tables each having a subset of the attributes of . If one of the tables in the join has all the attributes of the table , the join ...