MYSQL中统计查询结果总行数的便捷方法省去count(*)_MySQL

例如：

SELECT SQL_CALC_FOUND_ROWS tid FROM cdb_threads WHERE fid=14 LIMIT 1,10;

假设满足条件的有1000条，这里返回10条。
立即使用

SELECT found_rows() AS rowcount;

则返回的 rowcount 为1000；
这样节省了SELECT count(*) AS rowcount的重复查询，可以节省比较可观的时间。

以下是该放在在游味中的应用：

function mail_list_sent( $uid, $start ) {
// 注意SQL_CALC_FOUND_ROWS uid之间没有逗号
$query = "SELECT SQL_CALC_FOUND_ROWS uid, real_name, current_city, msg_uid, sender_flag, ".
"msg_title, msg_content FROM " . TT_DBTABLEPRE . "mailbox as mb1, " . TT_DBTABLEPRE .
"user as usr1 WHERE mb1.sender_id=usr1.uid AND mb1.sender_id=$uid AND sender_flag > 0 LIMIT $start, " . TT_PAGESIZE;
$mails = $this->db->fetch_all( $query );
//查询SELECT中满足条件的行数，与LIMIT子句无关
$max_count = $this->db->fetch_first( "SELECT found_rows() AS rowcount" );
$tmp['state_code'] = 200;
$tmp['info'] = "OK";
$tmp['list'] = $mails;
$data = json_encode( $tmp );
return $data;
}
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