Oracle: Delete all constraint from multiple table

If you want o delete all constraint from your required tables , you can use following PL/SQL program:

begin
    for r in ( select table_name, constraint_name
               from user_constraints
               where TABLE_NAME in ('TABLE1', 
                                    'TABLE2',
                                    'TABLE3') )
    loop
        execute immediate 'alter table '||r.table_name
                          ||' drop constraint '||r.constraint_name;
    end loop;
end loop;