MySQL refinement of query - mysql

Question

I'm uing the following query to give me a set of the last 20 matches for a team. I want to find their goals scored in the last 20 matches and order the results by (goals scored, date):
SELECT * FROM (
SELECT *, `against` AS `goalsF` , `for` AS `goalsA`
FROM `matches` , `teams` , `outcomes`
WHERE(
`home_team_id`=7 AND `matches`.away_team_id = `teams`.team_id
OR
`away_team_id`=7 AND `matches`.home_team_id = `teams`.team_id
)
AND `matches`.score_id = `outcomes`.outcome_id
ORDER BY `date` DESC
LIMIT 0 , 20
) res
ORDER BY `goalsF`
The problem is that:
if the team we're looking up is the home team, we need to count "goalsfor".
if the team ins the away team we need to count "goalsagainst" to find their for goals.
So what I need to be able to do is something like:
if (`home_team_id`=7 AND `matches`.away_team_id = `teams`.team_id)
SELECT *, `for` AS `goalsF` , `against` AS `goalsA`
if (`away_team_id`=7 AND `matches`.home_team_id = `teams`.team_id)
SELECT *, `against` AS `goalsF` , `for` AS `goalsA`
But, this must be peformed on the sub-set or results. I'm not sure if this is even possible, but it is beyond my knowledge of MYSQL.
Any help would be hugely appreciated.
Alan.

Answer 1

First, you really need to learn ANSI standard join syntax, where you put the join conditions in an on clause rather than a from clause. Also, aliases may a query much more readable.
The following does the logic that you want, although it does not include the team names:
SELECT *
FROM (SELECT *,
(case when m.home_team_id = 7 then o.against end) as `goalsF` ,
(case when m.away_team_id = 7 then o.`for` end) as `goalsA`
FROM `matches` m join
`outcomes` o
on m.score_id = o.outcome_id
WHERE m.home_team_id = 7 or m.away_team_id = 7
ORDER BY `date` DESC
LIMIT 0 , 20
) res
ORDER BY `goalsF`
To get the team names, you should join twice to the teams table, once for the home team and once for the away team. You can do this either in the subquery or afterwards. It is also a good idea to explicit mention the columns you are choosing and to include a table alias on every column reference:
SELECT *
FROM (SELECT m.*, o.*,
homet.team_name as hometeam_name, awayt.team_name as away_team_name,
(case when m.home_team_id = 7 then o.against end) as `goalsF` ,
(case when m.away_team_id = 7 then o.`for` end) as `goalsA`
FROM `matches` m join
`outcomes` o
on m.score_id = o.outcome_id join
teams homet
on homet.team_id = m.home_team_id join
teams awayt
on awayt.team_id = m.away_team_id
WHERE m.home_team_id = 7 or m.away_team_id = 7
ORDER BY `date` DESC
LIMIT 0 , 20
) res
ORDER BY `goalsF`
EDIT:
To get just goals for team 7, you can use:
(case when m.home_team_id = 7 then o.`for`
when m.away_team_id = 7 then o.against
end) as goals
To get goals for the other team:
(case when m.home_team_id = 7 then o.against
when m.away_team_id = 7 then o.`for`
end) as goals
EDIT II:
To get the "other" team name, the logic is similar. Replace the team name references in the select with:
(case when m.home_team_id = 7 then awayt.team_name
when m.away_team_id = 7 then homet.team_name
end) as goals