Check Foreign key exists in MySQL

If you want to add/drop foreign key then you need to check is foreign key is exist or not.

IF NOT EXISTS (SELECT NULL FROM information_schema.TABLE_CONSTRAINTS WHERE
                   CONSTRAINT_SCHEMA = DATABASE() AND
                   CONSTRAINT_NAME   = 'fk_rabbits_main_page' AND
                   CONSTRAINT_TYPE   = 'FOREIGN KEY') THEN
   ALTER TABLE `rabbits` ADD CONSTRAINT `fk_rabbits_main_page`
                             FOREIGN KEY (`main_page_id`)
                             REFERENCES `rabbit_pages` (`id`);
END IF

Using following query you will get more information about foreign key with column details.

 SELECT 
    TABLE_NAME,COLUMN_NAME,
    CONSTRAINT_NAME,
    REFERENCED_TABLE_NAME,
    REFERENCED_COLUMN_NAME 
FROM 
    INFORMATION_SCHEMA.KEY_COLUMN_USAGE 
WHERE 
    TABLE_NAME='TABLENAME' 
    AND REFERENCED_TABLE_NAME = 'REFERENCED_TABLE_NAME' 
    AND CONSTRAINT_NAME='FK_Key_Name'
    AND REFERENCED_COLUMN_NAME='Code';