MySQL 5.7 Reference Manual Including MySQL NDB Cluster 7.5 and NDB Cluster 7.6
The TABLE_CONSTRAINTS table describes
which tables have constraints.
The TABLE_CONSTRAINTS table has these
columns:
CONSTRAINT_CATALOG
The name of the catalog to which the constraint belongs. This
value is always def.
CONSTRAINT_SCHEMA
The name of the schema (database) to which the constraint belongs.
CONSTRAINT_NAME
The name of the constraint.
TABLE_SCHEMA
The name of the schema (database) to which the table belongs.
TABLE_NAME
The name of the table.
CONSTRAINT_TYPE
The type of constraint. The value can be
UNIQUE, PRIMARY KEY,
FOREIGN KEY, or CHECK.
This is a CHAR (not
ENUM) column. The
CHECK value is not available until MySQL
supports CHECK.
The UNIQUE and PRIMARY
KEY information is about the same as what you get
from the Key_name column in the output from
SHOW INDEX when the
Non_unique column is 0.