Question related to jsp , my SQL

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MySQL

JSP

i have two table in first table there is two coloumn central_id_no, name, and in second table there is four coloumn central_id_no,name,address,central_id_no1 i am showing central_id_no on page from first table and i am inserting data in second table first table central_id_no is updating with second table central_id_no 1
but problem id duplicate no is occuring means two person assinging same central _id_no
it should not be i want unique central_id _no assign to indivisual person

What I have tried:

i have two table in first table there is two coloumn central_id_no, name, and in second table there is four coloumn central_id_no,name,address,central_id_no1 i am showing central_id_no on page from first table and i am inserting data in second table first table central_id_no is updating with second table central_id_no 1
but problem id duplicate no is occuring means two person assinging same central _id_no
it should not be i want unique central_id _no assign to indivisual person