Select distinct values from 1 column

问题:

I want to select distinct values from only one column (the BoekingPlaatsId column) with this query:

SELECT MAX(BoekingPlaatsId), BewonerId, Naam, VoorNaam
FROM table
GROUP BY BewonerId, Naam, VoorNaam

How do I do that in SQL Server?

回答1:

DISTINCT should work if you just want the user names:

SELECT DISTINCT BewonerId, Naam, Voornaam
FROM TBL

but if you need the minimum ID values, group by the names...

SELECT MIN(BoekingPlaatsId), MIN(BewonerId), Naam, Voornaam
FROM TBL
GROUP BY Naam, Voornaam

回答2:

I think you should be able to use

SELECT DISTINCT BewonerId, Naam, VoorNaam

You can't add BoekingPlaatsId, because:

• DISTINCT looks for unique rows
• You need to specify what BoekingPlaatsId value you want
  (In case of Jan Janssens, do you want BoekingPlaatsId 1 or 2?)

What also works is this:

SELECT MAX(BoekingPlaatsId), BewonerId, Naam, VoorNaam
FROM ...
GROUP BY BewonerId, Naam, VoorNaam

回答3:

I don't do alot of this so i'm not 100% certain of the syntax so you may need to tweak it slightly, google rank over and partition. Try this...

SELECT 
    *,
    RANK() OVER(PARTITION BY Naam  order by Naam ) as Rank
FROM
    TABLE
WHERE 
    Rank = 1

This is overkill for a 4 column table, but if you have a fairly denormalised table with alot of columns, this approach is invaluable for select distinct on 1 column.

回答4:

I think what you're looking for is something like this:

select distinct column1 from table1 where column2 = (select distinct column2 from table1)

回答5:

select Naam, Voornaam, min(BewonerId), min(BoekingPlaatsId) from tableName
group by Naam, Voornaam

回答6:

just group By those 2 columns

  Select Min(BoekingPlaatsId), Min(bewonerId), naam, voornaam
  from table
  group By naam, voornaam

回答7:

This is how you can select from a table with only unique values for your column:

CREATE VIEW [yourSchema].[v_ViewOfYourTable] AS
WITH DistinctBoekingPlaats AS
(
    SELECT [BewonerId], 
           [Naam],
           [VoorNaam],
           [BoekingPlaatsId],
           ROW_NUMBER() OVER(PARTITION BY [BoekingPlaatsId] ORDER BY DESC) AS 'RowNum'
    FROM [yourSchema].[v_ViewOfYourTable]
)
SELECT * 
FROM DistinctProfileNames
WHERE RowNum = 1
--if you would like to apply group by you can do it in this bottom select clause but you don't need it to gather distinct values 

You don't need group by to accomplish this.

回答8:

I ran into a similar problem and for me the solution was using the GROUP BY clause. So basically, I grouped all the blogs with same title as one group.

Syntax:

SELECT post_title, post_link
FROM blogs
WHERE [ conditions ]
GROUP BY post_title
ORDER BY post_title;

Maybe you are grouping multiple columns

回答9:

Sounds like you want something like

select distinct(BewonerId), Naam, Voornaam from table_name