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In a relational database, the schema defines the tables, fields, relationships, views, indexes, packages, procedures, functions, queues, triggers, types, sequences, materialized views, synonyms, database links, directories, XML schemas, and other elements. A database generally stores its schema in a data dictionary. Although a schema is defined ...
A Bachman diagram is a certain type of data structure diagram, [2] and is used to design the data with a network or relational "logical" model, separating the data model from the way the data is stored in the system. The model is named after database pioneer Charles Bachman, and mostly used in computer software design.
A conceptual schema or conceptual data model is a high-level description of informational needs underlying the design of a database. [1] [2] It typically includes only the core concepts and the main relationships among them. This is a high-level model with insufficient detail to build a complete, functional database. [3]
Set up the table relationships – Look at each table and decide how the data in one table is related to the data in other tables. Add fields to tables or create new tables to clarify the relationships, as necessary. Refine the design – Analyze the design for errors. Create tables and add a few records of sample data.
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]
Entity relationship diagram, essential for the design of database tables, extracts, and metadata. [16] A data dictionary or database dictionary is a file that defines the basic organization of a database. [16]
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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.