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
Evaluate these two SQL statements: SELECT last_name, salary , hire_date FROM EMPLOYEES ORDER BY salary DESC; SELECT last_name, salary , hire_date FROM EMPLOYEESORDER BY 2 DESC; What is true about them?（）
A.The two statements produce identical results.
B.The second statement returns a syntax error.
C.There is no need to specify DESC because the results are sorted in descending order by default.
D.The two statements can be made to produce identical results by adding a column alias for the salary column in the second SQL statement. -
单项选择题
Which SQL statement accepts user input for the columns to be displayed, the table name, and the WHERE condition?（）
A.SELECT &1, "&2" FROM &3 WHERE last_name = '&4';
B.SELECT &1, '&2' FROM &3 WHERE '&last_name = '&4'';
C.SELECT &1, &2 FROM &3 WHERE last_name = '&4';
D.SELECT &1, '&2' FROM EMP WHERE last_name = '&4'; -
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));
