oracle pl sql ora,的Oracle SQL Developer：PL/SQL：ORA-00903：无效的表名

Error starting at line 2 in command:

BEGIN

DELETE * FROM book_copies;

DELETE * FROM books;

/* more code here */

END;

Error report:

ORA-06550: line 2, column 10:

PL/SQL: ORA-00903: invalid table name

ORA-06550: line 2, column 3:

PL/SQL: SQL Statement ignored

ORA-06550: line 3, column 10:

PL/SQL: ORA-00903: invalid table name

ORA-06550: line 3, column 3:

PL/SQL: SQL Statement ignored

06550. 00000 - "line %s, column %s:\n%s"

*Cause: Usually a PL/SQL compilation error.

*Action:

正如我在数据库中存在两个表这是荒谬的。我可以这样做：

SELECT * FROM books;

或者：

SELECT * FROM book_copies;

而且他们两个的工作。

为什么Oracle SQL Developer会说“无效的表名”？