column "activiteit.straat" must appear in the GROUP BY clause or be used in an aggregate function

Question

So I need to have the name as a column and then also street but it doesn't work.

I tried this

SELECT naam, straat FROM activiteit GROUP BY naam HAVING COUNT(*)>1;

expected to have this

naam | straat |         
--------+--------+
 tennis  | Gent   |  
 basket  | Antwerpen  |  

but got this

column "activiteit.straat" must appear in the GROUP BY clause or be used in an aggregate function

Answer 1

If you have multiple streets for every name, yove to decide which tio take A MIN MAX or any other aggregation function will do

the following will show you all streets with the same name

SELECT naam, string_agg(istinct straat , ',') as straat
FROM activiteit 
GROUP BY naam 
HAVING COUNT(*)>1;