MYSQL限制返回意外结果

Question

<?php
$quuuu = mysql_query("SELECT * FROM products limit 9,15 ") or die("Query Error");
while($ffff=mysql_fetch_array($quuuu)){
    echo "<li><a href='view.php?id=" . $ffff['id'] . "'>" . $ffff['title'] . "</a></li>";
}
echo mysql_num_rows($quuuu);
?>

its should return (7), and the result is (15)

Answer 1

See the doc, https://dev.mysql.com/doc/refman/5.0/en/select.html .

The LIMIT clause can be used to constrain the number of rows returned by the SELECT statement. LIMIT takes one or two numeric arguments, which must both be nonnegative integer constants (except when using prepared statements).

With two arguments, the first argument specifies the offset of the first row to return, and the second specifies the maximum number of rows to return.

So with your query,

SELECT * FROM products limit 9,15

You are telling mysql to return fifteen rows starting at the tenth row. You are getting 15 from echo mysql_num_rows($quuuu); because there are 15 rows. Why do you expect 7 to be outputted?

Also note that the mysql_ driver is depreciated, you should switch over to PDO or mysqli . They have a lot more useful features.

http://php.net/manual/en/migration55.deprecated.php

The original MySQL extension is now deprecated, and will generate E_DEPRECATED errors when connecting to a database. Instead, use the MySQLi or PDO_MySQL extensions.

http://php.net/manual/en/book.mysqli.php
http://php.net/manual/en/ref.pdo-mysql.php

Answer 2

Your LIMIT use is wrong.

Syntax: limit start_at, amount_of_records

If you want 7 elements starting at 15th element, you should use

SELECT * from products limit 14, 7