key_column_usage

key_column_usage identifies all columns that are restricted by some unique, primary key, or foreign key constraint.

The following fields are provided in key_column_usage:

Field	Description
CONSTRAINT_CATALOG	The name of the catalog to which the constraint belongs. This value is always def.
CONSTRAINT_SCHEMA	The name of the database to which the constraint belongs.
CONSTRAINT_NAME	The name of the constraint.
TABLE_CATALOG	The name of the catalog to which the table belongs. This value is always def.
TABLE_SCHEMA	The name of the database to which the table belongs.
TABLE_NAME	The name of the table that has the constraint.
COLUMN_NAME	The name of the column that has the constraint.If the constraint is a foreign key, then this is the column of the foreign key, not the column that the foreign key references.
ORDINAL_POSITION	The column's position within the constraint, not the column's position within the table. Column positions are numbered beginning with 1.
POSITION_IN_UNIQUE_CONSTRAINT	NULL for unique and primary-key constraints. For foreign-key constraints, this column is the ordinal position in key of the table that is being referenced.
REFERENCED_TABLE_SCHEMA	The name of the schema referenced by the constraint.
REFERENCED_TABLE_NAME	The name of the table referenced by the constraint.
REFERENCED_COLUMN_NAME	The name of the column referenced by the constraint.