add column if not exists mysql
SELECT count(*) INTO @EXIST
FROM INFORMATION_SCHEMA.COLUMNS
WHERE TABLE_SCHEMA = 'mydatabase'
AND COLUMN_NAME = 'mycolumn'
AND TABLE_NAME = 'mytable' LIMIT 1;
SET @query = IF (@exist <= 0, 'ALTER TABLE mydatabase.`mytable` ADD COLUMN `mycolumn` MEDIUMTEXT NULL',
'select ' COLUMN EXISTS' status');
PREPARE stmt FROM @query;
EXECUTE stmt;