Select distinct on one column with multiple columns returned sql server

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sql server - How to efficiently check EXISTS on multiple columns? - Database Administrators Stack Exchange

  http://dba.stackexchange.com/questions/19344/how-to-efficiently-check-exists-on-multiple-columns
Single Aggregate Query SELECT MAX(CASE WHEN B IS NULL THEN 1 ELSE 0 END) AS B, MAX(CASE WHEN C IS NULL THEN 1 ELSE 0 END) AS C FROM T This could process both columns at the same time so have a worst case of one full scan. SELECT TOP 2 * FROM (SELECT DISTINCT CASE WHEN b IS NULL THEN NULL ELSE 'foo' END AS b , CASE WHEN c IS NULL THEN NULL ELSE 'bar' END AS c FROM test T WHERE LEFT(b,1) + LEFT(c,1) IS NULL ) AS DT Edit 2 One last tweak that occurred to me is that the query above could still end up processing more rows than necessary in the event that the first row it encounters with a NULL has NULLs in both column B and C

SQL SELECT with DISTINCT on multiple columns - w3resource

  http://www.w3resource.com/sql/select-statement/queries-with-distinct-multiple-columns.php
See the following presentation : Pictorial presentation : Go Top SELECT with DISTINCT on multiple columns and ORDER BY clause You can use an order by clause in select statement with distinct on multiple columns

SELECT DISTINCT on one column, with multiple columns returned, ms access query

  http://www.experts-exchange.com/Database/MS_Access/Q_28357107.html
But what if you absolutely need that value in your dataset? I recently ran into this problem, and no matter what I tried, I could not get a particular field into a dataset and keep the rest of the recordset updateable, without using a DLookup(). But if you want to see what happened last month, you have to open the query and type in the range, or -- if you're using fields on a form to supply your query with criteria -- enter the dates before you run the query

SQL DISTINCT on Multiple Columns

  http://www.sqlservercentral.com/Forums/Topic1060020-2810-1.aspx
I did my my first one yesterday and actually as a result learnt some things that I didn't know - which is always a bonus - and got some quality feedback from some very wise and kind folks. A minor section on performance may have been beneficial but it is not critical, as the article is aimed at novice users and getting them to start writing SQL

SQL Server Forums - Using DISTINCT with multiple columns?

  http://www.sqlteam.com/forums/topic.asp?TOPIC_ID=58896
The reason it returns multiple rows is because the COMPLETE row is NOT distinct, adding those other fields makes it UNIQUE.What you want to read over is GROUP BY vs

sql - SELECT DISTINCT on multiple columns - Database Administrators Stack Exchange

  http://dba.stackexchange.com/questions/102677/select-distinct-on-multiple-columns
Detailed explanation in my go-to answer for this technique: Optimize GROUP BY query to retrieve latest record per user I updated ypercube's SQL Fiddle and added mine to the playlist. Actually Jack's query results are a bit better than shown above (if we remove the order by) and can be further improved by removing the 4 internal distinct and leaving only the external one

SQL DISTINCT on Multiple Columns - SQLServerCentral

  http://www.sqlservercentral.com/articles/DISTINCT/71551/
The user could end up un-knowingly using completely incorrect SUM had he used the result from the second query if the requirement was to get the SUM of unique values of ReorderPoint