在SQL查询中使用Distinct

Question

Please find the query given below:

SELECT DISTINCT 
        reco_index_content_code,
        reco_index_content_name,
        reco_index_content_url
    FROM tbl_reco_index_contents
    WHERE
        reco_index_user_action_at_select = 1
        AND user_profile_number = 1

I need to select reco_index_content_name as distinct.

How should the above query be modified, in order to accomplish that, such that there are no duplicate reco_index_content_name rows ?

Answer 1

The standard solution is documented and uses an uncorrelated subquery as follows:

SELECT x.* 
  FROM my_table x
  JOIN 
     ( SELECT grouping_id
            , MIN(ordering_id) min_ordering_id 
         FROM my_table 
        GROUP 
           BY grouping_id  
     ) y
    ON y.grouping_id = x.grouping_id
   AND y.min_ordering_id = x.ordering_id;