PL/SQL块中只能直接嵌入SELECT,DML(INSERT,UPDATE,DELETE)以及事务控制语句(COMMIT,ROLLBACK,SAVEPOINT),而不能直接嵌入DDL语句(CREATE,ALTER,DROP)和DCL语句(GRANT,REVOKE)-PL/SQL block can only be embedded directly in the SELECT, DML (INSERT, UPDATE, DELETE), and transaction control statements (COMMIT, ROLLBACK, SAVEPOINT,) can not be directly embedded DDL statements (CREATE, ALTER, DROP) and DCL statements (GRANT, REVOKE)