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一个distinct问题引发的思考

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Release： 2016-06-07 17:40:31
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今天被人问到这样一个问题，整理出来给大家也参考一下 假设有如下这样一张表格： 这里的数据，具有如下的特征： 在一个DepartmentId中，可能会有多个Name，反之也是一样。就是说Name和DepartmentId是多对多的关系 。 现在想实现这样一个查询： 按照Departmen

今天被人问到这样一个问题，整理出来给大家也参考一下

假设有如下这样一张表格：

image

这里的数据，具有如下的特征：在一个DepartmentId中，可能会有多个Name，反之也是一样。就是说Name和DepartmentId是多对多的关系。

 

现在想实现这样一个查询：按照DepartmentID排完序之后（第一步），香港空间，再获取Name列的不重复值（第二步），香港服务器租用，而且要保留在第一步后的相对顺序。以本例而言，美国空间，应该返回三个值依次是：ACB

 

 

我们首先会想到下面这样一个写法

DepartmentId

 

Related labels：
distinct think question
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