How to count all records but only retrieve (LIMIT)

问题:

I want to echo only the first 10 rows, but I need to count the total number of rows affected by the query.

I was doing a LIMIT 10 and then counting with the obvious problem I kept getting 10 as the count.

What would be a proper way to do it?

$data = mysql_query("SELECT * FROM Badges WHERE UID = '$user' ORDER by Date DESC");
$count = mysql_num_rows($data);

while($row = mysql_fetch_array( $data )) 
    { 
    echo $row['Site'];
    }

回答1:

MySQL has some special support for this sort of thing. First, include SQL_CALC_FOUND_ROWS in your SELECT:

SELECT SQL_CALC_FOUND_ROWS *
FROM Badges
WHERE UID = '$user'
ORDER by Date DESC
LIMIT 10 -- Or whatever

Then pull out your rows and then immediately look at FOUND_ROWS() like this:

SELECT FOUND_ROWS()

to get the number of rows that matched your original query without considering the LIMIT clause.

This is MySQL-specific but it should be a little faster than doing two queries.

回答2:

It's pretty standard to issue two queries, one selecting the desired columns with the limit clause and another selecting only a count with no limit.

For example

$countQuery = 'SELECT COUNT(1) FROM Badges WHERE UID = ?';
$limitQuery = 'SELECT * FROM Badges WHERE UID = ? ORDER BY `Date` DESC LIMIT 0, 10';

回答3:

You have to make 2 queries: the first one will count all rows, the second one will return 10 rows:

$count = 0;
$query = "SELECT count(*) as count FROM Badges WHERE UID = '$user'";
$rs = mysql_query($query);   

if (mysql_errno() == 0)
{
    $r = mysql_fetch_object($rs);
    $count = $r->count;
}

if ($count > 0)
{
    $query = "SELECT * FROM Badges WHERE UID = '$user' ORDER by Date DESC LIMIT 10";
    $rs = mysql_query($query);      

    if (mysql_errno() == 0)
    {            
        while ($r = mysql_fetch_array($rs))       
        {       
            echo $r['Site']; 
        }     
    }
}

回答4:

count all records

$data = mysql_query("SELECT * FROM Badges WHERE UID = '$user' ORDER by Date DESC");
$count = mysql_num_rows($data);
echo "No of Records is :" . $count;

print 10 records...

 $data = mysql_query("SELECT * FROM Badges WHERE UID = '$user' ORDER by Date DESC LIMIT 0, 10");
    while($row = mysql_fetch_array( $data )) 
        { 
        echo $row['Site'];
        }