从列中选择唯一值

Question

我有一个MySQL表,其中包含以下类型的信息:

    Date            product 
2011-12-12           azd
2011-12-12           yxm
2011-12-10           sdx
2011-12-10           ssdd  

以下是我用来从此表中获取数据的脚本示例:

<?php

$con = mysql_connect("localhost","username","password");
if (!$con)
  {
  die('Could not connect: ' . mysql_error());
  }
mysql_select_db("db", $con);
$sql=mysql_query("SELECT * FROM buy ORDER BY Date");
while($row = mysql_fetch_array($sql))
{

 echo "<li><a href='http://www.website/". $row['Date'].".html'>buy ". date("j, M Y", strtotime($row["Date"]))."</a></li>";

    }
    mysql_close($con);
?> 

此脚本显示表中的每个日期,例如

12.dec 2011
12.dec.2011
10.dec.2011
10.dec.2011

我想只显示独特的日期,例如

12.dec.2011
10.dec.2011

Answer 1

在MySQL中使用DISTINCT运算符:

SELECT DISTINCT(Date) AS Date FROM buy ORDER BY Date DESC;

Answer 2

使用

SELECT DISTINCT Date FROM buy ORDER BY Date

所以MySQL删除了重复项

顺便说SELECT一下:当你从MySQL获得大量结果时,在PHP中使用显式列名更少的资源

Answer 3

使用此查询获取值

SELECT * FROM `buy` group by date order by date DESC

Answer 4

其余几乎是正确的,除了他们应该由Date DESC订购

SELECT DISTINCT(Date) AS Date FROM buy ORDER BY Date DESC;

Answer 5

DISTINCT始终是获得独特价值的正确选择.您也可以在不使用它的情况下进行替换.那是GROUP BY.它只是在查询结尾添加,后跟列名.

SELECT * FROM buy GROUP BY date,description