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The database schema is the structure of a database described in a formal language supported typically by a relational database management system (RDBMS). The term " schema " refers to the organization of data as a blueprint of how the database is constructed (divided into database tables in the case of relational databases ).
The SQL/Schemata, or Information and Definition Schemas, part of the SQL standard is defined by ISO/IEC 9075-11:2008. SQL/Schemata defines the information schema and definition schema , providing a common set of tools to make SQL databases and objects self-describing.
The Suppliers and Parts database is an example relational database that is referred to extensively in the literature [citation needed] and described in detail in C. J. Date's An Introduction to Database Systems, 8th ed. [1] It is a simple database comprising three tables: Supplier, Part and Shipment, and is often used as a minimal exemplar of the interrelationships found in a database.
[5] [6] A relational database definition (database schema, sometimes referred to as a relational schema) can thus be thought of as a collection of named relation schemas. [7] [8] In implementations, the domain of each attribute is effectively a data type [9] and a named relation schema is effectively a relation variable (relvar for short).
A table in a SQL database schema corresponds to a predicate variable; the contents of a table to a relation; key constraints, other constraints, and SQL queries correspond to predicates. However, SQL databases deviate from the relational model in many details, and Codd fiercely argued against deviations that compromise the original principles. [3]
In the context of SQL, data definition or data description language (DDL) is a syntax for creating and modifying database objects such as tables, indices, and users. DDL statements are similar to a computer programming language for defining data structures, especially database schemas. Common examples of DDL statements include CREATE, ALTER ...
Snowflake schema used by example query. The example schema shown to the right is a snowflaked version of the star schema example provided in the star schema article. The following example query is the snowflake schema equivalent of the star schema example code which returns the total number of television units sold by brand and by country for 1997.
Pages in category "Articles with example SQL code" The following 28 pages are in this category, out of 28 total. ... Set operations (SQL) Snowflake schema; SQL; SQL ...