-- Add blood_group column to students table
ALTER TABLE students ADD COLUMN blood_group VARCHAR(10) NULL DEFAULT NULL AFTER gender;

-- Add comment for the column
ALTER TABLE students MODIFY blood_group VARCHAR(10) NULL DEFAULT NULL COMMENT 'Blood group of the student (e.g., A+, B-, O+, AB-)';

-- Sample data for testing (optional)
-- UPDATE students SET blood_group = 'O+' WHERE id = 1;
-- UPDATE students SET blood_group = 'A-' WHERE id = 2;