Select * with one Group By Column in SQL

Question

I want to select * from a table and group by only one column. I am new to SQL, so a basic questions. My query looks like this.

Select top 10
    [DocumentClass], [DocumentUID]
    ,[DocumentClassification]
    ,[DocumentNumber]
    ,[Revision]
    ,[Description]
    ,[Owner]
from 
    Table
Group BY 
    [DocumentClass]

Error I am getting:

Column 'DocumentUID' is invalid in the select list because it is not contained in either an aggregate function or the GROUP BY clause.

Please advise. Thanks

Answer 1

If you want to get one row per document class, then use row_number() instead of group by :

Select top 10 t.*
from (select t.*, row_number() over (partition by documentclass order by newid()) as seqnum
      from table t
     ) t
where seqnum = 1;

row_number() is a function that enumerates the rows. In this case, each document class will start over. newid() is just a way of choosing a random row.

Normally, when you use group by , you would also have aggregation functions such as min() or sum() .

Answer 2

This error means the SQL Server doesn't know which column do you want to use. When you use GROUP BY command you want to select one specific value ( MIN, SUM, or AVG) or u want all ( count that rows ) . You get all necessary information from this site. GROUP BY