Examine the following command that is executed for the TRANSPORT table in the SH schema:


SQL>SELECT DBMS_STATS.CREATE_EXTENDED_STATS('sh', 'customers_obe', '(country_id,cust_state_province)') FROM dual;

Which statement describes the significance of this command?

A. It collects statistics into the pending area in the data dictionary.

B. It creates a virtual hidden column in the CUSTOMERS_OBE table.

C. It collects statistics with AUTO_SAMPLE_SIZE for ESTIMATE_PERCENT.

D. It creates a histogram to hold skewed information about the data in the columns.

答案：（B）

解析：

DBMS_STATS.CREATE_EXTENDED_STATS,为用户指定的表中的列组或表达式在系统中创建列statistics entry.

当用户或自动统计信息收集作业收集表的统计信息时,这个扩展的统计信息将被收集.

这种统计信息称为"extended statistics"