Finding the average and display the maximum average of duplicate ids?

For this, use AVG(). To find the maximum average value, use MAX() and group by id. Let us first create a table −

mysql> create table DemoTable
   -> (
   -> PlayerId int,
   -> PlayerScore int
   -> );
Query OK, 0 rows affected (0.55 sec)

Insert some records in the table using insert command −

mysql> insert into DemoTable values(1,78);
Query OK, 1 row affected (0.16 sec)
mysql> insert into DemoTable values(2,82);
Query OK, 1 row affected (0.25 sec)
mysql> insert into DemoTable values(1,45);
Query OK, 1 row affected (0.17 sec)
mysql> insert into DemoTable values(3,97);
Query OK, 1 row affected (0.22 sec)
mysql> insert into DemoTable values(2,79);
Query OK, 1 row affected (0.12 sec)

Display all records from the table using select statement −

mysql> select *from DemoTable;

This will produce the following output −

+----------+-------------+
| PlayerId | PlayerScore |
+----------+-------------+
|       1 |           78 |
|       2 |           82 |
|       1 |           45 |
|       3 |           97 |
|       2 |           79 |
+----------+-------------+
5 rows in set (0.00 sec)

Here is the query to find the maximum average value for duplicate ids in MySQL −

mysql> select PlayerId from DemoTable
   -> group by PlayerId
   -> having avg(PlayerScore) > 80;

This will produce the following output −

+----------+
| PlayerId |
+----------+
|        2 |
|        3 |
+----------+
2 rows in set (0.00 sec)