สอบถามเรื่องการ COUNT แบบมีเงื่อนไขเวลาเป็นช่วงเวลา PHP + MySQL

$sql = "SELECT node,count(case when TIMESTAMPDIFF(MINUTE,timefail,timeup) > 30 and causename='OFC ขาด/Fiber ขาด' then failid end) as cnt ";
$sql .= "FROM fail_dslam where failid <> 0 group by node having cnt <> 0 order by failid asc";

SELECT `failid` , node, timefail, (

SELECT timefail
FROM fail_dslam
WHERE failid < a.failid
AND causename = 'OFC ขาด/Fiber ขาด'
ORDER BY failid ASC
LIMIT 0 , 1
) AS difTimeFail, TIMESTAMPDIFF(
MINUTE , timefail, (

SELECT timefail
FROM fail_dslam
WHERE failid > a.failid
AND causename = 'OFC ขาด/Fiber ขาด'
ORDER BY failid ASC
LIMIT 0 , 1
) ) AS DiffTime
FROM fail_dslam AS a
WHERE causename = 'OFC ขาด/Fiber ขาด'
ORDER BY failid ASC

SELECT `failid` , node, timefail, (

SELECT timefail
FROM fail_dslam
WHERE failid < a.failid
AND causename = 'OFC ขาด/Fiber ขาด'
ORDER BY failid ASC
LIMIT 0 , 1
) AS difTimeFail, TIMESTAMPDIFF(
MINUTE , timefail, (

SELECT timefail
FROM fail_dslam
WHERE failid > a.failid
AND causename = 'OFC ขาด/Fiber ขาด'
ORDER BY failid ASC
LIMIT 0 , 1
) ) AS DiffTime
FROM fail_dslam AS a
WHERE causename = 'OFC ขาด/Fiber ขาด'-- group by note

HAVING DiffTime >30
ORDER BY failid ASC

SELECT `failid`, note, timefail, 
(select timefail from fail_dslam where failid < a.failid AND causename='OFC ขาด/Fiber ขาด' order by failid asc limit 0,1) as difTimeFail, 
TIMESTAMPDIFF(MINUTE,timefail, (select timefail from fail_dslam where failid > a.failid AND causename='OFC ขาด/Fiber ขาด' order by failid asc limit 0,1)) AS DiffTime,
count(*) AS cnt
FROM fail_dslam as a 
where causename='OFC ขาด/Fiber ขาด'  
GROUP by note 
HAVING DiffTime > 30
ORDER by failid asc