The Information Schema REFERENTIAL_CONSTRAINTS table contains information about foreign keys. The single columns are listed in the KEY_COLUMN_USAGE table.
It has the following columns:
| Column | Description |
|---|---|
CONSTRAINT_CATALOG |
Always def. |
CONSTRAINT_SCHEMA |
Database name, together with CONSTRAINT_NAME identifies the foreign key. |
CONSTRAINT_NAME |
Foreign key name, together with CONSTRAINT_SCHEMA identifies the foreign key. |
UNIQUE_CONSTRAINT_CATALOG |
Always def. |
UNIQUE_CONSTRAINT_SCHEMA |
Database name, together with UNIQUE_CONSTRAINT_NAME and REFERENCED_TABLE_NAME identifies the referenced key. |
UNIQUE_CONSTRAINT_NAME |
Referenced key name, together with UNIQUE_CONSTRAINT_SCHEMA and REFERENCED_TABLE_NAME identifies the referenced key. |
MATCH_OPTION |
Always NONE. |
UPDATE_RULE |
The Update Rule; one of CASCADE, SET NULL, SET DEFAULT, RESTRICT, NO ACTION. |
DELETE_RULE |
The Delete Rule; one of CASCADE, SET NULL, SET DEFAULT, RESTRICT, NO ACTION. |
TABLE_NAME |
Table name from the TABLE_CONSTRAINTS table. |
REFERENCED_TABLE_NAME |
Referenced key table name, together with UNIQUE_CONSTRAINT_SCHEMA and UNIQUE_CONSTRAINT_NAME identifies the referenced key. |
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https://mariadb.com/kb/en/information-schema-referential_constraints-table/