我有一张桌子,上面写着菜单。其中只有 5 条记录可用,但我需要超过 5 条记录,包括重复记录。
实际场景,一群人可以点相同的菜单,例如如果我有
1)tea
->foo
->bar
2)coffee
->latte
->expresso
3)shake
两人或多人可以点咖啡。
我尝试这样做
$menu = RestaurantsMenu::where('tag','=','Coffee')
->get()
->random(5);
菜单
标签
菜单 1 鸡肉
菜单 2 素食
菜单 3 鸡肉
你可以看到我有两种鸡,如果我想随机取出4只鸡,包括重复的鸡,我该怎么做?请指教。
问题在写作时更新了,我对问题的解释可能不正确 - 现在就保留它
原始解释:如果数据库中的行数少于X行,如何通过随机复制其他行来创建具有X个条目的结果集。
原答案:
这种重复应该在查询完现有数据后仅使用 PHP 来完成。
我会使用一个函数来获取查询和所需的结果数量,然后从现有的行中随机创建足够的行。
function fillResultsWithDuplicates($query, $numRowsNeeded) {
// avoid querying _more_ than needed when you have sufficient
$res = $query->random($numRowsNeeded);
// may need to coerce into an array - not familiar with laravel
return fillArrayWithRandomDuplicates($res, $numRowsNeeded);
}
function fillArrayWithRandomDuplicates($vals, $numEntriesNeeded) {
/*im sure this can be written to be faster and more succinct
could accept an optional function to perform the filling*/
if (count($vals) >= $numEntriesNeeded) return $vals;
$numDuplicatesNeeded = $numEntriesNeeded - count($vals);
$dupes = [];
// Here your are pulling random values from your array to act as duplicates needed
for ($i = 0; $i < $numDuplicatesNeeded; $i++) {
$dupes[] = $vals[mt_rand(0, count($vals)-1)]; // array_rand could be used as well but may be slower
}
// Maybe shuffle as well if you need
return array_merge($dupes, $vals);
}
您的情况的用法
$menu = RestaurantsMenu::where('tag','=','Coffee')->get()
$filledMenu = fillResultsWithDuplicates($menu, 5);
使用简单数组的演示:
$initial = ["a", "b", "c"];
$filled = fillArrayWithRandomDuplicates($initial, 10);
// will contain 7 random selections of a,b,c followed by original a,b,c for total 10 entries
// ex: bcaaabaabc - add shuffles as needed