Need to convert date to word using trigger
Based on your comment, the trigger has multiple lines.

You need a BEGIN...END block as follows:

USE mcet
DELIMITER $$
DROP TRIGGER IF EXISTS tg_student_details_insert;
CREATE TRIGGER tg_student_details_insert BEFORE INSERT
ON student_details FOR EACH ROW
BEGIN
    SET NEW.created_date = NOW();
    SET NEW.dobw = date_to_words(NEW.dob);
END;
DELIMITER ;


You answered this question before (How to autoincrement Prod_id based on Product_Name using trigger in mysql). In that post, you used a BEGIN...END block for four(4) lines of code. You needed one for this post as well.