semicolon ';' is the default sqlterminator mostwidely
used. if you change sqlterminator to tilde '~'  you
must use '~' to terminate the sql. This has nothing to
do with DDL statemnts or DML staments.
SQL> select * from dept;

    DEPTNO DNAME          LOC
---------- -------------- -------------
        10 ACCOUNTING     NEW YORKS
        20 RESEARCH       DALLAS
        30 SALES          CHICAGO
        40 OPERATIONS     BOSTON

SQL> set sqlterminator '~'
SQL> select * from dept;
  2  /
select * from dept;
                  *
ERROR at line 1:
ORA-00911: invalid character

SQL> select * from dept~

    DEPTNO DNAME          LOC
---------- -------------- -------------
        10 ACCOUNTING     NEW YORKS
        20 RESEARCH       DALLAS
        30 SALES          CHICAGO
        40 OPERATIONS     BOSTON