mysql particular query [closed] - mysql

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Closed 10 years ago.
I have two table: teams and formations:
Table teams:
team_id | team_name
1 | Barcelona
2 | Real Madrid
3 | PSG
Table formations:
formation_id | team_id | module
1 | 2 | 5-3-2
2 | 1 | 4-4-2
3 | 3 | 4-4-2
4 | 2 | 4-4-3
Pratically i have need of "join" between the 2 table GROUP BY team_id but with the last "formation_id"
The result my be this:
team_id | team_name | formation_id | module
1 | Barcelona | 2 | 4-4-2
2 | Real Madrid| 4 | 4-4-3
3 | PSG | 3 | 4-4-2
Actually my query is:
SELECT *
FROM formations f
INNER JOIN teams t
ON (f.team_id = t.team_id)
GROUP BY t.team_id
With my query I selected the first insert formation for each team, instead I must select the last formations for each team.

Answer 1

Check this SQLFIDDLE
SELECT A.team_id,A.team_name,B.formation_id,B.module
FROM teams A,formations B
WHERE A.team_id=B.team_id
AND B.formation_id =
(
SELECT max(formation_id)
FROM formations C
WHERE C.team_id =B.team_id
)
ORDER BY A.team_id;
create table teams
(
team_id int
,team_name varchar(40)
);
create table formations
(
formation_id int
,team_id int
,module int
);
insert into teams
values
(1,'Barcelona'),(2,'Real Madrid'),(3,'PSG');
insert into formations
values
(1,2,532),(2,1,442),(3,3,442),(4,2,443);

Answer 2

You can find their maximum formation ID using a subquery that you will later join it with the original tables. Try this one,
SELECT a.*, c.formation_ID, c.`module`
FROM teams a
INNER JOIN
(
SELECT team_id, MAX(formation_ID) maxID
FROM formations
GROUP BY team_ID
) b ON a.team_id = b.team_id
INNER JOIN formations c
ON c.team_id = b.team_id AND
c.formation_ID = b.maxID
ORDER BY a.Team_id
SQLFiddle Demo

Answer 3

You can write:
SELECT t.team_id,
t.team_name,
f.formation_id,
f.module
FROM teams t
JOIN formations f
ON f.team_id = t.team_id
-- require f.formation_id to be MAX(formation_id) for some team:
JOIN ( SELECT MAX(formation_id) AS id
FROM formations
GROUP
BY team_id
) max_formation_ids
ON max_formation_ids.id = f.formation_id
;
or:
SELECT t.team_id,
t.team_name,
f.formation_id,
f.module
FROM teams t
JOIN formations f
ON f.team_id = t.team_id
-- require f.formation_id to be MAX(formation_id) for this team:
WHERE f.formation_id =
( SELECT MAX(formation_id)
FROM formations
WHERE team_id = t.team_id
)
;
or:
SELECT t.team_id,
t.team_name,
f.formation_id,
f.module
FROM teams t
JOIN formations f
ON f.team_id = t.team_id
-- forbid f.formation_id to be less than another for the same team:
LEFT
OUTER
JOIN formations f2
ON f2.team_id = t.team_id
AND f2.formation_id > f.formation_id
WHERE f2.formation_id IS NULL
;

Answer 4

SQL spec states that when you use group by clause then all fields/expressions in the output should be either results of aggregate functions (like count, avg, etc) or fields listed in group by clause. otherwise the behavior is not defined. So if you need to pick exactly this record you need to add some criteria to your query. Also, there is no guarantee that simple 'select * from some_table' would always return rows in the same order.

Answer 5

You could do something like:
select f.*, t.team_name from formations f
join (select team_id, max(formation_id) as max_formation_id from formations f
group by team_id) as mrf on mrf.max_formation_id = f.formation_id
join teams t on f.team_id = t.team_id

Answer 6

This version produces the same result without aggregates, which often incur internal sorting.
SELECT t.team_id,
t.team_name,
f.formation_id,
f.module
FROM teams t
INNER JOIN formations f
ON f.team_id = t.team_id
LEFT OUTER JOIN formations f2
ON f2.team_id = t.team_id
AND f2.formation_id > f.formation_id
WHERE f2.formation_id IS NULL

Answer 7

create table teams (team_id integer, team_name varchar(50));
create table formations (formation_id integer, team_id integer, module varchar(20));
insert into formations (formation_id, team_id, module) values
(1, 2, '5-3-2'),
(2, 1, '4-4-2'),
(3, 3, '4-4-2'),
(4, 2, '4-4-3')
;
insert into teams (team_id, team_name) values
(1, 'Barcelona'),
(2, 'Real Madrid'),
(3, 'PSG')
;
select t.team_id, team_name, f.formation_id, module
from
formations f
inner join
teams t on f.team_id = t.team_id
inner join (
select team_id, max(formation_id) as formation_id
from formations
group by team_id
) s on s.team_id = t.team_id and s.formation_id = f.formation_id
order by t.team_id
;
+---------+-------------+--------------+--------+
| team_id | team_name | formation_id | module |
+---------+-------------+--------------+--------+
| 1 | Barcelona | 2 | 4-4-2 |
| 2 | Real Madrid | 4 | 4-4-3 |
| 3 | PSG | 3 | 4-4-2 |
+---------+-------------+--------------+--------+