单项选择题
A. The inner query always sorts the results of the outer query
B. The outer query always sorts the results of the inner query
C. The outer query must return a value to the outer query
D. The inner query returns a value to the outer query
E. The inner query must always return a value or the outer query will give an error
单项选择题 What is true about sequences? （）
单项选择题 Examine the structure of the EMPLOYEES table: EMPLOYEE_ID NUMBER Primary Key FIRST_NAME VARCHAR2 (25) LAST_NAME VARCHAR2 (25) HIRE_DATE DATE Which UPDATE statement is valid? （）
单项选择题 Examine the statement: Create synonym emp for hr. employees; What happens when you issue the statement? （）