key-column-usage-transact-sql.md

title	KEY_COLUMN_USAGE (Transact-SQL) | Microsoft Docs
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ms.date	03/15/2017
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KEY_COLUMN_USAGE (Transact-SQL)

[!INCLUDEtsql-appliesto-ss2008-asdb-xxxx-xxx-md]

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 ** Do not use INFORMATION_SCHEMA views to determine the schema of an object. The only reliable way to find the schema of a 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 ** Do not use INFORMATION_SCHEMA views to determine the schema of an object. The only reliable way to find the schema of a 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)