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2. Cardinality (data modeling) - Wikipedia

   en.wikipedia.org/wiki/Cardinality_(data_modeling)

   Within data modelling, cardinality is the numerical relationship between rows of one table and rows in another. Common cardinalities include one-to-one , one-to-many , and many-to-many . Cardinality can be used to define data models as well as analyze entities within datasets.

3. One-to-many (data model) - Wikipedia

   en.wikipedia.org/wiki/One-to-many_(data_model)

   In systems analysis, a one-to-many relationship is a type of cardinality that refers to the relationship between two entities (see also entity–relationship model).For example, take a car and an owner of the car.

4. One-to-one (data model) - Wikipedia

   en.wikipedia.org/wiki/One-to-one_(data_model)

   A country has only one capital city, and a capital city is the capital of only one country. (Not valid for some countries).. In systems analysis, a one-to-one relationship is a type of cardinality that refers to the relationship between two entities (see also entity–relationship model) A and B in which one element of A may only be linked to one element of B, and vice versa.

5. Many-to-many (data model) - Wikipedia

   en.wikipedia.org/wiki/Many-to-many_(data_model)

   For example, think of A as Authors, and B as Books. An Author can write several Books, and a Book can be written by several Authors. In a relational database management system, such relationships are usually implemented by means of an associative table (also known as join table, junction table or cross-reference table), say, AB with two one-to-many relationships A → AB and B → AB.

6. Relational model - Wikipedia

   en.wikipedia.org/wiki/Relational_model

   The purpose of the relational model is to provide a declarative method for specifying data and queries: users directly state what information the database contains and what information they want from it, and let the database management system software take care of describing data structures for storing the data and retrieval procedures for ...

7. Snowflake schema - Wikipedia

   en.wikipedia.org/wiki/Snowflake_schema

   The snowflake schema is in the same family as the star schema logical model. In fact, the star schema is considered a special case of the snowflake schema. The snowflake schema provides some advantages over the star schema in certain situations, including: Some OLAP multidimensional database modeling tools are optimized for snowflake schemas. [3]