What is complex table?
The answer to your question is already covered in our study material. Follow the given link and scroll down to the topic 'Complex tables'.
https://www.meritnation.com/cbse/class11-commerce/studymaterial/economics/statistics-for-economics/presentation-of-data/443_2496_6427#slide2_tabular-presentation-of-data
https://www.meritnation.com/cbse/class11-commerce/studymaterial/economics/statistics-for-economics/presentation-of-data/443_2496_6427#slide2_tabular-presentation-of-data