How can I drop a “not null” constraint in Oracle when I don't know the name of the constraint?

Question

I have a database which has a NOT NULL constraint on a field, and I want to remove this constraint. The complicating factor is that this constraint has a system-defined nam

Answer 1

Something like that happened to me when I made copies of structures to temporary tables, so I removed the not null.

DECLARE
   CURSOR cur_temp_not_null IS
        SELECT table_name, constraint_name  FROM all_constraints WHERE table_name LIKE 'TEMP_%' AND  owner='myUSUARIO';

   V_sql VARCHAR2(200); 

BEGIN
  FOR c_not_null IN cur_temp_not_null
   LOOP
     v_sql :='ALTER TABLE ' || c_not_null.table_name || ' DROP CONSTRAINT '|| c_not_null.constraint_name;
     EXECUTE IMMEDIATE  v_sql;     
  END LOOP;
END;