System Catalog Views

Applies to: SQL Server 2022, SQL Server 2019, SQL Server 2017, SQL Server 2016, Azure SQL Database, Azure Synapse Analytics, SQL Server Analysis Services, SQL Server Reporting Services, Parallel Data Warehouse

System catalog views provide metadata about the objects in a SQL Server instance. They are a critical part of understanding and managing your databases. These views offer detailed information about tables, columns, stored procedures, user-defined functions, indexes, and much more.

Overview of System Catalog Views

System catalog views are organized into schemas, primarily:

• sys: Contains views that expose information about SQL Server system objects.
• INFORMATION_SCHEMA: Provides a standardized way to access metadata, following the SQL standard.

Commonly Used Catalog Views

sys.objects

Returns a row for each schema-scoped object in an instance of SQL Server. This view lists objects like tables, views, stored procedures, and functions.

SELECT
    name,
    type_desc,
    create_date,
    modify_date
FROM
    sys.objects
WHERE
    type = 'U' -- User table
ORDER BY
    name;

sys.columns

Contains a row for each column of each object in the instance of SQL Server. It provides information about column names, data types, nullability, and default constraints.

SELECT
    c.name AS ColumnName,
    t.name AS TableName,
    ty.name AS DataType,
    c.max_length,
    c.is_nullable
FROM
    sys.columns AS c
JOIN
    sys.tables AS t ON c.object_id = t.object_id
JOIN
    sys.types AS ty ON c.user_type_id = ty.user_type_id
WHERE
    t.name = 'YourTableName' -- Replace with your table name
ORDER BY
    c.column_id;

sys.tables

Returns a row for each user table and system table in the instance of SQL Server.

SELECT
    name,
    object_id,
    create_date
FROM
    sys.tables
ORDER BY
    name;

INFORMATION_SCHEMA.COLUMNS

Provides a standardized view of column metadata. It is useful for querying across different database systems.

SELECT
    TABLE_SCHEMA,
    TABLE_NAME,
    COLUMN_NAME,
    DATA_TYPE,
    IS_NULLABLE
FROM
    INFORMATION_SCHEMA.COLUMNS
WHERE
    TABLE_NAME = 'YourTableName' -- Replace with your table name
ORDER BY
    ORDINAL_POSITION;

Key Concepts

• Object ID (object_id): A unique identifier for each database object.
• Schema Name (schema_name): The name of the schema the object belongs to.
• Object Type (type, type_desc): Indicates the type of the object (e.g., 'U' for User Table, 'V' for View, 'P' for Stored Procedure).

Benefits of Using Catalog Views

• Performance: Optimized for querying metadata.
• Rich Information: Provide detailed and current information about database objects.
• Consistency: Offer a predictable structure for metadata access.
• Standardization: INFORMATION_SCHEMA views adhere to SQL standards, improving portability.

Further Reading

• Understanding Views
• Understanding Stored Procedures
• Understanding Indexes