select minute( now()-ins_time ) returning null - mysql

Question

I have a simple report that some users can run to check that we have received data from an external source. It counts the minutes since the last line was updated where INS_TIME is the time that the interface inserted the data.
Code below.
select minute( now()-ins_time ) as LastUpdateMinutes
from p_electro
order by ins_time desc limit 1
This works well and is used in a Crystal Report. However i am trying to make another one for a different table with a little extra complexity. I copied the above code and added to it as below.
select minute( now()-ins_time ) as LastUpdateMinutes
from p_treats
where location like '%e5%' and creator is null
order by ins_time desc limit 1
This criterion should basically indicate that the row was inserted by the interface and then reveal the minutes since the last one was entered. However when i run it, it runs successfully but i get a NULL returned (as below).
LastUpdateMinutes
-----------------
| NULL |
I was expecting to see thousands of minutes given we haven't received any data since 13.05.17 at 11am.
This works fine for the first table and has been in use for years.
To add some context, our data clerk runs this report twice a day and reports if the time in minutes is longer than 20 minutes. With the second table, we have not received data for 5 days (thanks to measures put in place after this cyber-attack) and it wasn't flagged up until the light bulb ignited in my head that this was probably affected.
I want to create another report for this table that we can add to the clerks daily checks and learn of missing data sooner
Anyone have any advice on why the second example doesn't work but the first example does? And how to fix it?
I have tried multiple syntax along the lines of:
SELECT
datediff(now(), ins_time) AS DiffDate
FROM
p_treats
WHERE
location LIKE 'e5%' and
creator is null
ORDER BY ins_time DESC
LIMIT 1
Which actually works to pull back the number of days and:
SELECT
timediff(now(), ins_time) AS DiffDate
FROM
p_hdtreatment
WHERE
hpwhere LIKE 'e5%' and
creator is null
ORDER BY ins_time DESC
LIMIT 1
Which returns the hours and this might actually have to be what we use, but i wanted to make it a little more accurate.
Thanks in advance

Answer 1

Try this.
SELECT TIMESTAMPDIFF(MINUTE, ins_time, now()) AS LastUpdateMinutes
from p_treats
where location like '%e5%'
and creator is null
order by ins_time desc limit 1
Checkout ->
MySQL TimeStampDiff
Side Note:
minute() used as it is in the first "working" example, I believe is giving you wrong answers.. minute() only pulls the Minute part of a date/time string out. Eg. SELECT MINUTE('2008-02-03 10:05:03') yields 5
Assuming "ins_time" is of data type "TimeStamp" or "DateTime", If the result of MINUTE(now() - ins_time) is greater then 1 hour, your answer is wrong. I would need to test this more to be sure.