一个distinct问题引发的思考
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：
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
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