2分层的SQL语句 [英] 2 tiered SQL statement
问题描述
我很新的SQL所以忍耐一下的话......我想从一个表调用任务分配,其中任务ID =(在另一个表中的所有任务ID,它的值为说,也许X选择电子邮件在一个名为列的项目ID。我希望只选择唯一的电子邮件。我想知道这是否可能在一个单一的sql语句?非常感谢任何帮助渲染!
I am quite new to SQL so bear with me for a moment... I wish to select email from a table called task allocation where task ID= (all the task ID in another table which has a value of say maybe X in a column called project ID. I wish to only select unique emails. May I know if this is possible in a single sql statement? Thanks a lot for any help rendered!
推荐答案
您可以使用查询设计窗口,逐步建立一个SQL语句。例如,你可以建立以下内容:
You can use the query design window to gradually build up an sql statement. For example, you can build the following:
SELECT DISTINCT TaskID From SomeTable WHERE ColX="X"
您可以通过右键单击DISTINCT关键字,选择属性,然后选择唯一的值。
You can get the DISTINCT keyword by right-clicking, choosing properties and selecting Unique Values.
您也可以建立:
SELECT Email From ATable As A
INNER JOIN SomeTable As B
ON a.TaskID = b.TaskID
现在替补:
SELECT Email From ATable As A
INNER JOIN (SELECT DISTINCT TaskID From SomeTable WHERE ColX="X") As B
ON a.TaskID = b.TaskID
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