单项选择题
The EMPLOYEES table has these columns:
LAST_NAME VARCHAR2(35)
SALARY NUMBER(8,2)
HIRE_DATE DATE
Management wants to add a default value to the SALARY column. You plan to alter the table by using this SQL statement:
ALTER TABLE EMPLOYEES
MODIFY (SALARY DEFAULT 5000);
Which is true about your ALTER statement?（）
A.Column definitions cannot be altered to add DEFAULT values.
B.A change to the DEFAULT value affects only subsequent insertions to the table.
C.Column definitions cannot be altered to add DEFAULT values for columns with a NUMBER data type.
D.All the rows that have a NULL value for the SALARY column will be updated with the value 5000.
相关考题
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单项选择题
Click the Exhibit button to examine the data of the EMPLOYEES table. Which statement lists the ID, name, and salary of the employee, and the ID and name of the employees manager, for all the employees who have a manager and earn more than 4000?（）
A.SELECT employee_id "Emp_id", emp_name "Employee", salary, employee_id "Mgr_id", emp_name "Manager" FROM employees WHERE salary > 4000;
B.SELECT e.employee_id "Emp_id", e.emp_name "Employee", e.salary, m.employee_id "Mgr_id", m.emp_name "Manager" FROM employees e JOIN employees m WHERE e.mgr_id = m.mgr_id AND e.salary > 4000;
C.SELECT e.employee_id "Emp_id", e.emp_name "Employee", e.salary, m.employee_id "Mgr_id", m.emp_name "Manager" FROM employees e JOIN employees m ON (e.mgr_id = m.employee_id) AND e.salary > 4000;
D.SELECT e.employee_id "Emp_id", e.emp_name "Employee", e.salary, m.mgr_id "Mgr_id", m.emp_name "Manager" FROM employees e SELF JOIN employees m WHERE e.mgr_id = m.employee_id AND e.salary > 4000;
E.SELECT e.employee_id "Emp_id", e.emp_name "Employee", e.salary, m.mgr_id "Mgr_id" m.emp_name "Manager" FROM employees e JOIN employees m USING (e.employee_id = m.employee_id) AND e.salary > 4000; -
单项选择题
A subquery can be used to（）.
A.create groups of data
B.sort data in a specific order
C.convert data to a different format
D.retrieve data based on an unknown condition -
单项选择题
Mary has a view called EMP_DEPT_LOC_VU that was created based on the EMPLOYEES, DEPARTMENTS, and LOCATIONS tables. She granted SELECT privilege to Scott on this view. Which option enables Scott to eliminate the need to qualify the view with the name MARY.EMP_DEPT_LOC_VU each time the view is referenced?（）
A.Scott can create a synonym for the EMP_DEPT_LOC_VU by using the command CREATE PRIVATE SYNONYM EDL_VU FOR mary.EMP_DEPT_LOC_VU; then he can prefix the columns with this synonym.
B.Scott can create a synonym for the EMP_DEPT_LOC_VU by using the command CREATE SYNONYM EDL_VU FOR mary.EMP_DEPT_LOC_VU; then he can prefix the columns with this synonym.
C.Scott can create a synonym for the EMP_DEPT_LOC_VU by using the command CREATE LOCAL SYNONYM EDL_VU FOR mary.EMP_DEPT_LOC_VU; then he can prefix the columns with this synonym.
D.Scott can create a synonym for the EMP_DEPT_LOC_VU by using the command CREATE SYNONYM EDL_VU ON mary(EMP_DEPT_LOC_VU); then he can prefix the columns with this synonym.
E.Scott cannot create a synonym because synonyms can be created only for tables.
F.Scott cannot create any synonym for Mary's view. Mary should create a private synonym for the view and grant SELECT privilege on that synonym to Scott.
