sparql select wikidata group_by and concat - group-by

Question

I want to extract a list o players and a list of clubs where it has played, separated by commas.
SELECT DISTINCT ?playerLabel
(GROUP_CONCAT(?teamLabel ; separator=',') as ?teams)
WHERE {
?player wdt:P106 wd:Q937857 .
?player wdt:P2574 ?team
SERVICE wikibase:label { bd:serviceParam wikibase:language "[AUTO_LANGUAGE],en". }
}
GROUP BY ?playerLabel
I have two problems:
I don't get a list of teams for each player, only the name, and variable ?teams empty.
If I don't use GROUP CONCAT and GROUP BY I obtain the team id, but I prefer the label of team.
For example 2 players...:
playerLabel teams
Cristiano Ronaldo Sporting Portugal, Manchester U, Real Madrid, Juventus, Manchester U
Leo Messi Barcelona, PSG
At least I need the Concat and group by, even with code...
thanks

Answer 1

You use P2574, which is "National-Football-Teams.com player ID". While National-Football-Teams.com lists all teams a player played for, this data is not accessible through the Wikidata Query Service. But Wikidata itself has a dedicated property for sports team member: P54.
So write ?player wdt:P54 ?team instead of ?player wdt:P2574 ?team.
Additionaly, you need to add ?team rdfs:label ?teamLabel . filter (lang(?teamLabel)='en') to be able to use ?teamLabel in GROUP_CONCAT().
Thus, the full working query looks like this (restricted to US players to avoid query time outs):
SELECT DISTINCT ?playerLabel (GROUP_CONCAT(?teamLabel ; separator=',') as ?teams)
WHERE {
?player wdt:P106 wd:Q937857 .
?player wdt:P27 wd:Q30 .
?player wdt:P54 ?team .
?team rdfs:label ?teamLabel . filter (lang(?teamLabel)='en')
SERVICE wikibase:label { bd:serviceParam wikibase:language "[AUTO_LANGUAGE],en". }
}
GROUP BY ?playerLabel