Data Dictionary in relational databases

Piotr Kononow - Dataedo Team Piotr Kononow 2018-09-30

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    I could argue that all database management systems (DBMS) have a thing called data dictionary. It is a set of views or tables that provide access to metadata about database schema - list of tables, columns, keys, etc. They are located in special system schema or are available implicitly in all schemas.

    Standard SQL data dictionary

    SQL-92 standard (for relational / SQL databases) specifies data dictionary called information schema. This standard defines tables data dictionary provides ..

    Proprietary data dictionary

    Most popular databases provide also their proprietary data dictionary, often referred to as System Catalog (or system views, system tables or simply catalog).

    Typical data in DBMS data dictionary

    Schema

    • Tables
    • Columns
    • Constraints
    • Foreign keys
    • Indexes
    • Sequences

    Programs

    • Views
    • User defined functions
    • Stored procedures
    • Triggers

    Security

    • Users
    • User groups
    • Privileges

    Physical implementation

    • Partitions
    • Files
    • Backups

    Storage

    • Size of tables and indexes in KBs
    • Number of rows in tables

    Auditing

    • Sessions
    • Connection history
    • Query history
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