126.View the Exhibit and examine the data in the PROJ_TASK_DETAILS table.

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本文介绍了一种SQL查询方法，用于生成项目任务依赖报告。该报告包含所有任务ID、它们所依赖的任务ID以及负责这些任务的员工姓名。通过使用LEFT OUTER JOIN操作，即使某些任务没有依赖项也能正确显示。

126.View the Exhibit and examine the data in the PROJ_TASK_DETAILS table.
The PROJ_TASK_DETAILS table stores information about tasks involved in a project and the relation
between them.
The BASED_ON column indicates dependencies between tasks. Some tasks do not depend on the
completion of any other tasks.
You need to generate a report showing all task IDs, the corresponding task ID they are dependent on, and
the name of the employee in charge of the task it depends on.
Which query would give the required result?

A.SELECT p.task_id, p.based_on, d.task_in_charge
FROM proj_task_details p JOIN proj_task_details d ON (p.based_on = d.task_id);
B.SELECT p.task_id, p.based_on, d.task_in_charge
FROM proj_task_details p LEFT OUTER JOIN proj_task_details d ON (p.based_on = d.task_id);
C.SELECT p.task_id, p.based_on, d.task_in_charge
FROM proj_task_details p FULL OUTER JOIN proj_task_details d ON (p.based_on = d.task_id);
D.SELECT p.task_id, p.based_on, d.task_in_charge
FROM proj_task_details p JOIN proj_task_details d ON (p.task_id = d.task_id);
答案：B
解析：首先应该知道条件应该是p.based_on = d.task_id，排除D，这里based_on可能为null，应此排除
A，c是full join连接，这里比如p02这个taskid，其实没有对应的based_on,但是这里 d.task_in_charge也会显示出来，
这里存在问题，所以排除C