php - MySQL/PHP 从多列中仅选择唯一值并将它们放入单独的数组中

Question

使用 PHP 和 MySQL，我尝试从表中的多个列(但不是表中的所有列)中选择唯一值，并将所选每列中的所有唯一值放入其自己的数组中。每列值的唯一性只能与同一列中的其他值进行比较。

下面的代码将所有列中的所有唯一值放入 $make_array 中，然后将空值放入所有其余数组中。

如何从这些列中仅选择唯一值并将每列值放入其自己的数组中？

$sql = "
    (SELECT make FROM items)
    UNION
    (SELECT model FROM items)
    UNION
    (SELECT year FROM items)
    UNION
    (SELECT month FROM items)
    UNION
    (SELECT day FROM items)
    UNION
    (SELECT hour FROM items)";

$result = @mysql_query($sql, $con) or die(mysql_error());

while($row = mysql_fetch_array($result)) {

    $make = $row[make];
    $model = $row[model];
    $year = $row[year];
    $month = $row[month];
    $day = $row[day];
    $hour = $row[hour];

    $make_array[make][] = $make;
    $model_array[model][] = $model;
    $year_array[year][] = $year;
    $month_array[month][] = $month;
    $day_array[day][] = $day;
    $hour_array[hour][] = $hour;
}

Answer 1

如果您想将其保留为一条 SQL 语句，那么您可以:

$sql = "
    SELECT DISTINCT 'make' as descr,make as val FROM items
    UNION
    SELECT DISTINCT 'model' as descr,model as val FROM items
    UNION
    SELECT DISTINCT 'year' as descr,year as val FROM items
    UNION
    SELECT DISTINCT 'month' as descr,month as val FROM items
    UNION
    SELECT DISTINCT 'day' as descr,day as val FROM items
    UNION
    SELECT DISTINCT 'hour' as descr,hour as val FROM items";

$result = @mysql_query($sql, $con) or die(mysql_error());

while($row = mysql_fetch_array($result)) {
    $make_array[$row['descr']][]=$row['val'];
}