View all foreign key constraints for entire MySQL database

You can use the INFORMATION_SCHEMA tables for this. For example, the INFORMATION_SCHEMA TABLE_CONSTRAINTS table.

Something like this should do it:

select *from INFORMATION_SCHEMA.TABLE_CONSTRAINTSwhere CONSTRAINT_TYPE = 'FOREIGN KEY'

This is what I prefer to get useful informations:

SELECT CONSTRAINT_NAME,       UNIQUE_CONSTRAINT_NAME,        MATCH_OPTION,        UPDATE_RULE,       DELETE_RULE,       TABLE_NAME,       REFERENCED_TABLE_NAMEFROM INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTSWHERE CONSTRAINT_SCHEMA = 'your_database_name'

The currently accepted answer by user RedFilter will work fine if you have just 1 database, but not if you have many.

After entering use information_schema; use this query to get foreign keys for name_of_db:

select * from `table_constraints` where `table_schema` like `name_of_db` and `constraint_type` = 'FOREIGN KEY'

Use this query to get foreign keys for name_of_db saved to world-writeable file output_filepath_and_name:

select * from `table_constraints` where `table_schema` like "name_of_db" and `constraint_type` = 'FOREIGN KEY' into outfile "output_filepath_and_name" FIELDS TERMINATED BY ',' ENCLOSED BY '"';