单项选择题
In which scenario would an index be most useful?（）
A.The indexed column is declared as NOT NULL.
B.The indexed columns are used in the FROM clause.
C.The indexed columns are part of an expression.
D.The indexed column contains a wide range of values.
相关考题
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单项选择题
What is true regarding subqueries?（）
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 inner 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
Examine the structure of the EMPLOYEES table: EMPLOYEE_ID NUMBER Primary Key FIRST_NAME VARCHAR2(25) LAST_NAME VARCHAR2(25) HIRE_DATE DATE You issue these statements: CREATE table new_emp ( employee_id NUMBER, name VARCHAR2(30)); INSERT INTO new_emp SELECT employee_id , last_name from employees; Savepoint s1; UPDATE new_emp set name = UPPER(name); Savepoint s2; Delete from new_emp; Rollback to s2; Delete from new_emp where employee_id =180; UPDATE new_emp set name = James; Rollback to s2; UPDATE new_emp set name = James WHERE employee_id =180; Rollback; At the end of this transaction, what is true?（）
A.You have no rows in the table.
B.You have an employee with the name of James.
C.You cannot roll back to the same savepoint more than once.
D.Your last update fails to update any rows because employee ID 180 was already deleted. -
多项选择题
Click the Exhibit button and examine the data in the EMPLOYEES table. Which three subqueries work? （）
A.SELECT * FROM employees where salary > (SELECT MIN(salary) FROM employees GROUP BY department_id);
B.SELECT * FROM employees WHERE salary = (SELECT AVG(salary) FROM employees GROUP BY department_id);
C.SELECT distinct department_id FROM employees WHERE salary > ANY (SELECT AVG(salary) FROM employees GROUP BY department_id);
D.SELECT department_id FROM employees WHERE salary > ALL (SELECT AVG(salary) FROM employees GROUP BY department_id);
E.SELECT last_name FROM employees WHERE salary > ANY (SELECT MAX(salary) FROM employees GROUP BY department_id);
F.SELECT department_id FROM employees WHERE salary > ALL (SELECT AVG(salary) FROM employees GROUP BY AVG(SALARY));
