[英]Select distinct values of distinct group
我有一個與此類似的表:
id title year
---------------
1 abc 1999
2 abc 2000
3 abc 2000
4 abc 1998
5 bce 1999
6 bce 1999
7 def 1999
8 def 1999
9 def 2000
我試圖得到一個類似於的數組
array('abc' => 'array(1999,2000,1998)', 'bce' => 'array(1999)', 'def' => 'array(1999, 2000)');
我知道很長一段時間,我認為它很耗時:
PHP:
$rid = mysql_query("SELECT DISTINCT title from table_name ORDER BY ASC);
while($arr = mysql_fetch_array($qr)){
$title = $arr
$rid = mysql_query("SELECT DISTINCT title from table_name ORDER BY ASC);
$yearArr = array();
while($arr2 = mysql_fetch_array($qr)){
$yearArr[] = $arr2['year'];
}
$finalArr = array(title => $yearArr);
}
最終,我得到了所要查找的數組,但是從上面的代碼中,如果我有1000個不同的標題,則整個過程將執行1001個查詢。 有什么簡短的方法嗎?
我也找到了一個類似的例子,但是,我無法走得更遠:
SELECT DISTINCT year,title FROM table_name WHERE title IN (SELECT DISTINCT title FROM papers_scanned_01) ORDER BY title ASC, year DESC
使用上面的查詢,我得到如下數組
array( [0] => 'abc', [1] => '1999', [2] => '2000', [3] => '1998', [4] => 'bce' and so on..
您可以使用以下代碼僅執行1條SQL即可獲得所需的數組
$sql = "SELECT title, group_concat(year) as years FROM table_name group by title"
$rs = mysql_query($sql);
$arr = array();
while($row = mysql_fetch_assoc($rs)) {
$arr[$row['title']] = explode(',',$row['years']);
}
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.