Mysql Query 使用单个查询从三个表中获取记录

Question

We have three table
table 1- app ( id , name )
table 2- appPlayer ( id , name )
table 3- appPlayerSession ( id , appId , appPlayerId , version)

my Current query is:

SELECT  (select name from app k where k.id= aps.appId) AS appName,version,appId,count(version) FROM appPlayerSession aps GROUP BY appId,version,appName

we need to count the session users for each game with same version, and also woth the object of all users data using single mysql query.

Current Result using my query, but we also need players for each app..

Answer 1

As you havent given your expected result and on basis of your requirement you can do something this.it may be enhanced as per your requirement.

SELECT  (select name from app k where k.id= aps.appId) AS appName,version,appId,(select P.name from appPlayer P where P.id=aps.appPlayerid) as appPlayerName, count(version) FROM appPlayerSession aps GROUP BY appId,version,appName,appPlayerName

Also check fiddle as per your requirement created as you havent given any data set and its on my assumption. http://sqlfiddle.com/#!9/30fe4f/1

New Sql as per your new added requirement-

select X.appname,X.version,X.appid,GROUP_CONCAT(distinct X.appPlayerName      order by X.appPlayerName) as Users ,
 sum(X.vercount) 
 from (SELECT  (select name from app k where k.id= aps.appId) 
 AS appName,version,appId,
 (select P.name from appPlayer P where P.id=aps.appPlayerid) 
 as appPlayerName, count(version)as vercount
 FROM appPlayerSession aps 
 GROUP BY appId,version,appName,appPlayerName) X
 group by X.appname,X.version,X.appid

New fiddle - http://sqlfiddle.com/#!9/13646c/5

Answer 2

You can use JOIN in sql to connect with multiple tables and fetch result

Below is the format :

SELECT t1.col, 
       t3.col 
FROM   table1 
       JOIN table2 
         ON table1.primarykey = table2.foreignkey 
       JOIN table3 
         ON table2.primarykey = table3.foreignkey 

In your case :

SELECT app.col, 
       appPlayer.col,
     appPlayerSession.col 
FROM   app 
       JOIN appPlayer 
         ON app.id = appPlayer.appId
       JOIN appPlayerSession 
         ON appPlayer.id = appPlayerSession.appPlayerId

Hope this is helpful.

One suggestion . It is not a standard to use camelCase for table and column names. snake_case is preferred widely.