Verificar que no exista una columna antes de añadirla

69_update_events_schema.sql

DELIMITER $$

DROP PROCEDURE IF EXISTS add_has_detail_column $$
CREATE PROCEDURE add_has_detail_column()
BEGIN

IF NOT EXISTS(SELECT * FROM information_schema.COLUMNS WHERE TABLE_SCHEMA=DATABASE() AND TABLE_NAME= 'events' AND COLUMN_NAME = 'has_detail') THEN
	ALTER TABLE `events` ADD COLUMN `has_detail` BOOLEAN NOT NULL DEFAULT 1 AFTER `is_migrated`;
END IF;

END $$

CALL add_has_detail_column() $$