[单选]

The CUSTOMERS table has these columns:
CUSTOMER_ID NUMBER (4) NOT NULL
CUSTOMER_NAME VARCHAR2 (100) NOT NULL
STREET_ADDRESS VARCHAR2 (150)
CITY_ADDRESS VARHCAR2 (50)
STATE_ADDRESS VARCHAR2 (50)
PROVINCE_ADDRESS VARCHAR2 (50)
COUNTRY_ADDRESS VARCHAR2 (50)
POSTAL_CODE VARCHAR2 (12)
CUSTOMER_PHONE VARCHAR2 (20)
The CUSTOMER_ID column is the primary key for the table.
You need to determine how dispersed your customer base is.
Which expression finds the number of different countries represented in the CUSTOMERS table?（）

Which statement describes the effect of the execution of the above PL/SQL block?（） The plan baselines are verified with the SQL profiles.。 All fixed plan baselines are converted into nonfixed plan baselines.。 All the nonaccepted SQL profiles are accepted into the plan baseline.。 The nonaccepted plans in the SQL Management Base are verified with the existing plan baselines.。 我国以私有制为基础的、完全意义上的税收制度正式确定的标志是（）。 夏朝的贡。 商朝的助。 周朝的彻。 春秋时期的初税亩。 2002年6月，《中小企业管理条例》正式颁布，它填补了我国中小企业立法的空白。 Which of the following storage systems uses both 2.5-inch and 3.5-inch SAS disk drives?（） XIV system 。 DS3500 。 DS3400 。 DS5100。 系统管理中UPS的维护管理属于（） 数据系统管理。 桌面系统管理。 环境系统管理。 硬件系统管理。

The CUSTOMERS table has these columns:
CUSTOMER_ID NUMBER (4) NOT NULL
CUSTOMER_NAME VARCHAR2 (100) NOT NULL
STREET_ADDRESS VARCHAR2 (150)
CITY_ADDRESS VARHCAR2 (50)
STATE_ADDRESS VARCHAR2 (50)
PROVINCE_ADDRESS VARCHAR2 (50)
COUNTRY_ADDRESS VARCHAR2 (50)
POSTAL_CODE VARCHAR2 (12)
CUSTOMER_PHONE VARCHAR2 (20)
The CUSTOMER_ID column is the primary key for the table.
You need to determine how dispersed your customer base is.
Which expression finds the number of different countries represented in the CUSTOMERS table?（）