MySQL 8.0 Reference Manual Including MySQL NDB Cluster 8.0
      The REFERENTIAL_CONSTRAINTS table
      provides information about foreign keys.
    
      The REFERENTIAL_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.
          UNIQUE_CONSTRAINT_CATALOG
        
          The name of the catalog containing the unique constraint that
          the constraint references. This value is always
          def.
        
          UNIQUE_CONSTRAINT_SCHEMA
        
The name of the schema containing the unique constraint that the constraint references.
          UNIQUE_CONSTRAINT_NAME
        
The name of the unique constraint that the constraint references.
          MATCH_OPTION
        
          The value of the constraint MATCH
          attribute. The only valid value at this time is
          NONE.
        
          UPDATE_RULE
        
          The value of the constraint ON UPDATE
          attribute. The possible values are CASCADE,
          SET NULL, SET DEFAULT,
          RESTRICT, NO ACTION.
        
          DELETE_RULE
        
          The value of the constraint ON DELETE
          attribute. The possible values are CASCADE,
          SET NULL, SET DEFAULT,
          RESTRICT, NO ACTION.
        
          TABLE_NAME
        
          The name of the table. This value is the same as in the
          TABLE_CONSTRAINTS table.
        
          REFERENCED_TABLE_NAME
        
The name of the table referenced by the constraint.