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042-103

原创 Linux操作系统 作者:jbymy2000 时间:2012-03-19 09:06:07 0 删除 编辑
103. View the Exhibit and examine the structure of EMPLOYEES and JOB_HISTORY
tables.The EMPLOYEES table maintains the most recent information regarding
salary, department, and job for all the employees. The JOB_HISTORY table
maintains the record for all the job changes for the employees. You want to
delete all the records from the JOB_HISTORY table that are repeated in the
EMPLOYEES table. Which two SQL statements can you execute to accomplish the
task? (Choose two.)
A. DELETE FROM job_history j
WHERE employee_id =(SELECT employee_id
FROM employees e WHERE j.employee_id = e.employee_id)
AND job_id = (SELECT job_id FROM employees e
WHERE j.job_id = e.job_id);
B. DELETE FROM job_history j
WHERE (employee_id, job_id) = ALL
(SELECT employee_id, job_id FROM employees e WHERE j.employee_id =
e.employee_id and j.job_id = e.job_id )
C. DELETE FROM job_history j WHERE employee_id =(SELECT employee_id
FROM employees e WHERE j.employee_id = e.employee_id and j.job_id =
e.job_id )
D. DELETE FROM job_history j
WHERE (employee_id, job_id) = (SELECT employee_id, job_id
FROM employees e WHERE j.employee_id = e.employee_id and j.job_id =
e.job_id )
Answer: CD
C,D是同一个意思,而A把删除范围扩大了

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