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PHP is an open source server-side scripting language that is widely used in the field of web development. Among them, database query is one of the important applications of PHP, and data grouping is one of the important operations of database query. This article will introduce the relevant knowledge and implementation methods of data grouping in PHP.
1. The concept of data grouping
Data grouping is to group data according to specified field values in order to better count, analyze and display data. In database queries, data grouping can be achieved through the GROUP BY clause. The field after the GROUP BY clause is the key to data grouping, and it is grouped according to it.
2. Syntax Example
The following is a syntax example to illustrate how to use the GROUP BY clause to group data:
SELECT column1, column2, …
FROM table_name
WHERE condition
GROUP BY column1, column2, …;
where column1, column2, … are the field names to be queried, table_name is the table name to be queried, condition is the query condition, GROUP column1, column2, ... after the BY clause are the fields to be grouped by.
3. How to implement data grouping
In PHP, you can use the mysql_query() function to execute the data grouping query statement, and then use the mysql_fetch_array() function to traverse the query results. The following is an example of a PHP program that implements data grouping:
$con = mysql_connect("localhost","username","password");
if (!$con )
{
die('Could not connect: ' . mysql_error());
}
mysql_select_db("mydatabase", $con);
$result = mysql_query( "SELECT city, COUNT(*) as count FROM customers GROUP BY city");
echo "
City | Count |
---|---|
" . $row['city'] . " | ";" . $row[ 'count'] . " | ";
?>
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