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.