图3列出了这个示例程序的类。

Figure 3 shows the classes of the example application.

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如果需要在修改列数据类型期间对数据库执行写访问，可以使用下一小节描述的ADMIN_MOVE_TABLE例程。

If you need to have write access to the database available while column data type is changed, you can use of ADMIN_MOVE_TABLE routine described in the next section.

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清单 4 显示了除使用静态列外，还可以向帐户编号字段添加简单验证例程以确保输入值不是非数字值。

Listing 4 shows an example of the power of adding a simple validation routine to the account number field to make sure it cannot be a non-number in addition to using static columns.

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