How Can I Select Only Unique Dates from a MySQL Database Table Using PHP?

Selecting Unique Values from a Column

In a scenario where you have a table with duplicated values in a specific column, extracting only the unique values can be crucial for data integrity and efficient processing.

Consider a MySQL table that stores sales data, with each row representing a product purchased on a particular date:

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

To retrieve all dates from this table using PHP, the following script can be utilized:

<?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);
?>

However, this script would produce a list with duplicate dates due to the nature of the data stored in the 'Date' column. To limit the results to unique dates only, we can employ MySQL's DISTINCT operator:

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

In this query, the DISTINCT operator is applied to the 'Date' column, ensuring that only unique values are returned. The 'AS Date' clause assigns the alias 'Date' to the distinct values, which can then be referenced in subsequent clauses. By adding 'ORDER BY Date DESC', the results are sorted in descending order.

By incorporating this modified query into your PHP script, you can extract a list of only the unique dates from the table, avoiding duplicates and ensuring data accuracy.

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