A convenient way to count the total row number of query results in MySQL save count (*)

Look at the manual found that the role of sql_calc_found_rows keyword in the query to meet the filter conditions after the total number of results (not limited by the Limit) specific use of the following, interested friends can learn under

MySQL's keywords:
Sql_calc_found_rows
After viewing the manual, it is found that this keyword is useful when querying the total number of results (not limited by Limit) that meet the filter criteria.

For example:

Copy Code code as follows:


SELECT sql_calc_found_rows tid from cdb_threads WHERE fid=14 LIMIT 1, 10;

Let's say there are 1000 conditions, and here we return 10.
Use now

Copy Code code as follows:


SELECT found_rows () as rowcount;

The returned rowcount is 1000;
This saves a significant amount of time by saving duplicate queries for select COUNT (*) as ROWCOUNT.

Here's how to put it in the swim flavor:

Copy Code code as follows:

Function Mail_list_sent ($uid, $start) {
//note there is no comma between sql_calc_found_rows uid
$query = "Select Sql_calc_f Ound_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);
//Query the number of rows in the select that satisfies the condition, regardless of the limit clause
$max _count = $this->db->fetch_first ("Select Found_rows () as rowcount"); br> $tmp [' state_code '] = 200;
$tmp [' info '] = "OK";
$tmp [' list '] = $mails;
$data = Json_encode ($tmp);
return $data;
}