problem in counting two fields in one query - php

Question

guys i need to count new private messages and old one from a table
so first thing come to mind is using mysql_num_rows and easy thing to do
// check new pms
$user_id = $userinfo['user_id'];
$sql = "SELECT author_id FROM bb3privmsgs_to WHERE user_id='$user_id' AND (pm_new='1' OR pm_unread='1')";
$result = $db->sql_query($sql) ;
$new_pms = $db->sql_numrows($result);
$db->sql_freeresult($result);
// check old pms
$sql = "SELECT author_id FROM bb3privmsgs_to WHERE user_id='$user_id' AND (pm_new='0' OR pm_unread='0')";
$result = $db->sql_query($sql) ;
$old_pms = $db->sql_numrows($result);
$db->sql_freeresult($result);
but how can i count these two fields just in one statement and shorter lines ?~

Answer 1

Use this query instead:
SELECT SUM(CASE WHEN pm_new = '1' OR pm_unread = '1' THEN 1 ELSE 0 END) AS new_pms,
SUM(CASE WHEN pm_new = '0' OR pm_unread = '0' THEN 1 ELSE 0 END) AS old_pms
FROM bb3privmsgs_to
WHERE user_id='$user_id'
Here's a MySQL-specific version that reads more cleanly:
SELECT COUNT(IF(pm_new = '1' OR pm_unread = '1', 1, NULL)) AS new_pms,
COUNT(IF(pm_new = '0' OR pm_unread = '0', 1, NULL)) AS old_pms
FROM bb3privmsgs_to
WHERE user_id='$user_id'

Answer 2

MySQL will cast comparisons to 1 or 0. You can use SUM() to add up the portion of the WHERE clause you were trying to count results for.
This is a (MySQL specific) shorter alternative to the CASE WHEN examples.
SELECT
SUM(pm_new='1' OR pm_unread='1') as new_pms,
SUM(pm_new='0' OR pm_unread='0') as old_pms
FROM bb3privmsgs_to
WHERE user_id='$userid'

Answer 3

In SQL Server, you can do something like this:
SELECT
SUM(CASE WHEN pm_new='1' OR pm_unread='1' THEN 1 ELSE 0 END),
SUM(CASE WHEN pm_new='0' OR pm_unread='0' THEN 1 ELSE 0 END)
FROM
bb3privmsgs_to WHERE user_id='$user_id'
I'll suppose you can do about the same thing in mySql, let me get back to you on the details...

Answer 4

As a lazy alternative to some of the other suggestions:
SELECT SUM(newPMS) AS newPMS,
SUM(oldPMS) AS oldPMS
FROM ( SELECT COUNT(author_id) AS newPMS,
0 AS oldPMS
FROM bb3privmsgs_to
WHERE user_id='$user_id'
AND (pm_new='1' OR pm_unread='1')
UNION
SELECT 0 AS newPMS
COUNT(author_id) AS oldPMS
FROM bb3privmsgs_to
WHERE user_id='$user_id'
AND (pm_new='0' OR pm_unread='0')
)