Random allocation until all options are used - php

Question

I have a table of available teams teams, with 24 different options.
I have another table entries, where each row is an allocation of one team to a user.
When an entry is created, a random team that has not been picked is allocated. However, if all the teams have been allocated (this can happen multiple times), only teams not yet allocated in this round of allocation are available.
For example, if my teams are A, B, C and D:
If there is an entry for A in entries, only B, C and D are available
If A, B, C and D have been picked, they are all available again
IF A has 3 entries, B has 3 entries, C has 2 entries and D has 2 entries, only C and D are available, until they all have the same number of entries
My code for this is convoluted:
//Make array of teams
for($i=1;$i<=24;$i++) $team[$i] = 1;
//Get entries from database
$stmt = $dbh->prepare("SELECT `team` FROM `entries`");
$stmt->execute();
$rows = $stmt->fetchAll(PDO::FETCH_ASSOC);
//Create array of available teams
$numRows = $stmt->rowCount();
while($numRows >= 24) {
for($i=1;$i<=24;$i++) {
$team[$i] = $team[$i]+1;
}
$numRows = $numRows - 24;
}
//Remove entries for teams in array
foreach($rows as $row) $team[$row["team"]] = $team[$row["team"]]-1;
foreach($team as $i => $v) if($v > 0) $available[] = $i;
There must be a more straightforward method to accomplish this; how can this be done?

Answer 1

The following gives you the number of assignments for each team:
SELECT team, COUNT(*) FROM entries GROUP BY team;
This gives you the minimum count for any team:
SELECT MIN(count) FROM (
SELECT COUNT(*) as count FROM entries GROUP BY team
)
To get the teams with the minimum count - those being available - but those two queries together into one:
SELECT teamcounts.team
FROM
(SELECT team, COUNT(*) as num FROM entries GROUP BY team) as teamcounts
WHERE
teamcounts.num = (
SELECT MIN(num) FROM (
SELECT COUNT(*) as num FROM entries GROUP BY team
) as tcounts
)
To get also those teams not yet included in entries we have to use the team table as well, removing all teams not currently available for selection:
SELECT teams.name
FROM teams
WHERE teams.name NOT IN (
SELECT teamcounts.team
FROM
(SELECT team, COUNT(*) as num FROM entries GROUP BY team) as teamcounts
WHERE
teamcounts.num != (
SELECT MIN(num) FROM (
SELECT COUNT(*) as num FROM entries GROUP BY team
) as tcounts
)
)

Answer 2

I haven't found a solution that works solely in SQL, however I've created the following query:
SELECT `id`, `num_selected` FROM
(SELECT `id`, SUM(is_selected) AS `num_selected` FROM
(SELECT t.`id`, CASE WHEN e.`team` IS NULL THEN 0 ELSE 1 END AS is_selected FROM `entries` e RIGHT JOIN `teams` t ON t.`id` = e.`team`)
AS `table1`
GROUP BY `id`)
AS `table2` GROUP BY `id` ORDER BY `num_selected` ASC, `id` ASC
This includes all the team rows that have NO entries yet, and the result is a table that has every team in one column, and alongside them is the number of selections.
Then, in PHP, I simply take the lowest value of selections (this will be the first row, as I've ordered by num_selected ASC) and only use other rows with that value as possible options:
$baseNum = $rows[0]["num_selected"];
foreach($rows as $row){
if($row["num_selected"]===$baseNum) $availableTeams[] = $row["id"];
}
However, ideally I'd have a solution that takes place solely in the SQL query!