如何使用distinct by order by子句 [英] how to use distinct with order by clause

问题描述

SELECT DISTINCT empid FROM empcdetails ORDER BY empdoj



执行上述声明它显示错误为休闲



错误



如果指定了SELECT DISTINCT，ORDER BY项必须出现在选择列表中




来自pradeep的

SELECT DISTINCT empid FROM empcdetails ORDER BY empdoj

executing the above statement it shows an error as fallows

Error

ORDER BY items must appear in the select list if SELECT DISTINCT is specified


from pradeep

推荐答案

是的，带有DISTINCT关键字的ORDER BY子句需要在选择列表如：

Yes, ORDER BY clause with DISTINCT keyword needs the column to be specified in the selection list like:

SELECT DISTINCT empid, empdoj FROM empcdetails ORDER BY empdoj

谢谢

Thanks

你不能订购你没有选择的东西，当你使用DISTINCT时，因为如果有两个具有不同empdoj值的empid，它如何知道如何订购它们？您还需要选择empdoj（这意味着它不会是明显的）或者您需要通过

You can''t order by something you did not select, when you use DISTINCT because if there''s two empids with different empdoj values, how does it know how to order them ? You need to select empdoj as well ( which means it won''t be distinct ) or you need to lose the order by

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