KEY_COLUMN_USAGE (Transact-SQL)
Applies to: 
SQL Server
Azure SQL Database
Azure SQL Managed Instance
Returns one row for each column that is constrained as a key in the current database. This information schema view returns information about the objects to which the current user has permissions.
To retrieve information from these views, specify the fully qualified name of INFORMATION_SCHEMA.view_name.
| Column name | Data type | Description |
|---|---|---|
| CONSTRAINT_CATALOG | nvarchar(128) | Constraint qualifier. |
| CONSTRAINT_SCHEMA | nvarchar(128) | Name of schema that contains the constraint. Important: Don't use INFORMATION_SCHEMA views to determine the schema of an object. INFORMATION_SCHEMA views only represent a subset of the metadata of an object. The only reliable way to find the schema of an object is to query the sys.objects catalog view. |
| CONSTRAINT_NAME | nvarchar(128) | Constraint name. |
| TABLE_CATALOG | nvarchar(128) | Table qualifier. |
| TABLE_SCHEMA | nvarchar(128) | Name of schema that contains the table. Important: Don't use INFORMATION_SCHEMA views to determine the schema of an object. INFORMATION_SCHEMA views only represent a subset of the metadata of an object. The only reliable way to find the schema of an object is to query the sys.objects catalog view. |
| TABLE_NAME | nvarchar(128) | Table name. |
| COLUMN_NAME | nvarchar(128) | Column name. |
| ORDINAL_POSITION | int | Column ordinal position. |
See Also
System Views (Transact-SQL)
Information Schema Views (Transact-SQL)
sys.columns (Transact-SQL)
sys.indexes (Transact-SQL)
sys.objects (Transact-SQL)
sys.foreign_keys (Transact-SQL)
sys.key_constraints (Transact-SQL)