how to delete colomn data?

Question

ID	name	Score	paper-II	image
1	vinod	12	paper-II	<binary data>
2	vinod	10	paper-I	null
3	vinod	0	paper-II	null
4	vinod	15	paper-I	<binary data>
5	vinod	12	paper-III	null
6	vinod	15	paper-IIII	<binary data>
7	vinod	16	paper-II	<binary data>
8	vinod	18	paper-II	null
9	vinod	13	paper-I	null

In Image column user did not upload image in first two or more times after that upload an image again user want to change that image so how delete first image and insert new image