MySQL: How to construct a given query - mysql

Question

I am not a MySQL guru at all, and I would really appreciate if someone takes some time to help me. I have three tables as shown below:
TEAM(teamID, teamName, userID)
YOUTH_TEAM(youthTeamID, youthTeamName, teamID)
YOUTH_PLAYER(youthPlayerID, youthPlayerFirstName, youthPlayerLastName, youthPlayerAge, youthPlayerDays, youthPlayerRating, youthPlayerPosition, youthTeamID)
And this is the query that I have now:
SELECT team.teamName, youth_team.youthTeamName, youth_player.*
FROM youth_player
INNER JOIN youth_team ON youth_player.youthTeamID = youth_team.youthTeamID
INNER JOIN team ON youth_team.teamID = team.teamID
WHERE youth_player.youthPlayerAge < 18
AND youth_player.youthPlayerDays < 21
AND youth_player.youthPlayerRating >= 5.5
What I would like to add to this query is a more thorough checks like the following:
if player has 16 years, and his position is scorer, then the player should have at least 7 rating in order to be returned
if player has 15 years, and his position is playmaker, then the player should have at least 5.5 rating in order to be returned
etc., etc.
How can I implement these requirements in my query (if possible), and is that query going to be a bad-way solution? Is it maybe going to be better if I do the selection with PHP code (if we suppose I use PHP) instead of doing it in the query?

Answer 1

Here is a possible solution with an additional "criteria/filter" table:
-- SAMPLE TEAMS: Yankees, Knicks:
INSERT INTO `team` VALUES (1,'Yankees',2),(2,'Knicks',1);
-- SAMPLE YOUTH TEAMS: Yankees Juniors, Knicks Juniors
INSERT INTO `youth_team` VALUES (1,'Knicks Juniors',1),(2,'Yankees Juniors',2);
-- SAMPLE PLAYERS
INSERT INTO `youth_player` VALUES
(1,'Carmelo','Anthony',16,20,7.5,'scorer',1),
(2,'Amar\'e','Stoudemire',17,45,5.5,'playmaker',1),
(3,'Iman','Shumpert',15,15,6.1,'playmaker',1),
(4,'Alex','Rodriguez',18,60,3.5,'playmaker',2),
(5,'Hiroki','Kuroda',16,17,8.7,'scorer',2),
(6,'Ichiro','Suzuki',19,73,8.3,'playmaker',2);
-- CRITERIA TABLE
CREATE TABLE `criterias` (
`id` int(11) NOT NULL,
`age` int(11) DEFAULT NULL,
`position` varchar(45) DEFAULT NULL,
`min_rating` double DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;
-- SAMPLE CRITERIAS
-- AGE=16, POSITION=SCORER, MIN_RATING=7
-- AGE=15, POSITION=PLAYMAKER, MIN_RATING=5.5
INSERT INTO `criterias` VALUES (1,16,'scorer',7), (2,15,'playmaker',5.5);
Now your query could look like:
SELECT team.teamName, youth_team.youthTeamName, youth_player.*
FROM youth_player
CROSS JOIN criterias
INNER JOIN youth_team ON youth_player.youthTeamID = youth_team.youthTeamID
INNER JOIN team ON youth_team.teamID = team.teamID
WHERE
(
youth_player.youthPlayerAge < 18
AND youth_player.youthPlayerDays < 21
AND youth_player.youthPlayerRating >= 5.5
)
AND
(
youth_player.youthPlayerAge = criterias.age
AND youth_player.youthPlayerPosition = criterias.position
AND youth_player.youthPlayerRating >= criterias.min_rating
)
This yields (shortened results):
teamName youthTeamName youthPlayerName Age Days Rating Position
=============================================================================
Yankees "Knicks Juniors" Carmelo Anthony 16 20 7.5 scorer
Yankees "Knicks Juniors" Iman Shumpert 15 15 6.1 playmaker
Knicks "Yankees Juniors" Hiroki Kuroda 16 17 8.7 scorer

Answer 2

Doing it in the query is quite fine...... as long as it doesn't get too messed up. You can perform a lot of stuff in your query, but it may get hard to maintain. So if it gets too long and you want somebody else to take a look at it, you should split it up or find a solution in your php-script.
As for your requirements add this too your WHERE-part:
AND
(
(YOUTH_PLAYER.youthPlayerAge >= 16 AND YOUTH_PLAYER.youthPlayerPosition = 'scorer' AND YOUTH_PLAYER.youthPlayerRating >= 7)
OR (YOUTH_PLAYER.youthPlayerAge >= 15 AND YOUTH_PLAYER.youthPlayerPosition = 'playmaker' AND YOUTH_PLAYER.youthPlayerRating >= 5.5)
)