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Data & Analytics · Foundational

Data Dictionary

A repository of metadata describing each table, column, data type, constraint and meaning in a database.

Definition

A data dictionary documents the technical structure of data and often includes descriptions, allowed values and owners. Databases keep an internal, active data dictionary in system catalogs such as INFORMATION_SCHEMA or Oracle's DBA_ views. Analysts use it to understand fields before querying.

Example

SELECT column_name, data_type FROM INFORMATION_SCHEMA.COLUMNS WHERE table_name = 'ORDERS';

Exam tip

A data dictionary is technical metadata; a business glossary defines business terms. Exams test the difference.

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