Delete the value of a field in a record

I know you came in from the title, but..., look below (not much content, no rush, no rush...)


(1) It's a good idea to delete the concept of "a data in a certain field", But the operation is not so direct delete, misuse this keyword, hehe! (Of course, it is only in the thinking stage, and people have not written sql "that"!!!)"
  delete from table name where field = a certain value -- that is, delete all records with a certain value in the field (2) If you actually want to For the operation of a certain field, then use update   update table name set field=null where field=a value--that is, replace the field in the table with a certain value with null or other magic horses