php - Updating custom table when user registers in WordPress -

i looking around code in wordpress , not sure , how complete doing.

i have custom table in wordpress have created, lets call mycustomtable. have data want insert in table when user registers.

i want add id auto increment , done table not problem, , want add in userid , hardcoded user group.

so when user registers following passed database.

insert mycustomtable values (this autoid not needed in insert, userid ,hardcoded membergroup); 

where or how this?

use user_register hook trigger.

if need custom queries, look here