MySQL Sub Query difficulty - mysql

Question

I'm trying to get a count of how many times a user has triggered the following query. And I've concluded that a Sub Query is required.
The below (admittedly indelicate) query works, as far as it goes, without the Sub Query. And the Sub Query works as a standalone query. But after three days of trying, I cannot get the two to work combined. I don't know if I have a glaring syntax error, or whether I'm getting it all wrong in principle. I need help!
SELECT id, status, FirstName, LastName, Track, KeyChange, Version,
DATE_FORMAT(CONVERT_TZ(Created,'+00:00','+1:00'), '%l:%i %p') AS Created_formatted,
TIME_FORMAT(SEC_TO_TIME(TIMESTAMPDIFF(SECOND, pinknoise.Created, CURRENT_TIMESTAMP() - INTERVAL '0' HOUR)),'%Hh %im') AS elapsed,
(SELECT `FirstName`, Count(*) AS 'CountRequests' FROM `pinknoise` GROUP by `FirstName`)
FROM pinknoise
WHERE status = 'incoming'
ORDER BY Created DESC

Answer 1

I don't really understand what your query should achieve, but well formatted it looks like:
SELECT
id,
status,
FirstName,
LastName,
Track,
KeyChange,
Version,
DATE_FORMAT(
CONVERT_TZ(
Created,
'+00:00',
'+1:00'
),
'%l:%i %p'
) AS Created_formatted,
TIME_FORMAT(
SEC_TO_TIME(
TIMESTAMPDIFF(
SECOND,
pinknoise.Created,
CURRENT_TIMESTAMP() - INTERVAL '0' HOUR
)
),
'%Hh %im'
) AS elapsed
(
SELECT
`FirstName`,
Count(*) AS 'CountRequests'
FROM
`pinknoise`
GROUP by
`FirstName`
)
FROM
pinknoise
WHERE
status = 'incoming'
ORDER BY
Created DESC
What I imagine: you want the number of total entries for this particular firstname in the same table. The dirty way would be:
SELECT
id,
status,
FirstName,
LastName,
Track,
KeyChange,
Version,
DATE_FORMAT(
CONVERT_TZ(
Created,
'+00:00',
'+1:00'
),
'%l:%i %p'
) AS Created_formatted,
TIME_FORMAT(
SEC_TO_TIME(
TIMESTAMPDIFF(
SECOND,
pinknoise.Created,
CURRENT_TIMESTAMP() - INTERVAL '0' HOUR
)
),
'%Hh %im'
) AS elapsed,
(
SELECT
Count(*)
FROM
`pinknoise` AS tb
WHERE
tb.FirstName = pinknoise.FirstName
) AS CountRequests
FROM
pinknoise
WHERE
status = 'incoming'
ORDER BY
Created DESC
A much better performance would have a join:
SELECT
pinknoise.id,
pinknoise.status,
pinknoise.FirstName,
pinknoise.LastName,
pinknoise.Track,
pinknoise.KeyChange,
pinknoise.Version,
DATE_FORMAT(
CONVERT_TZ(
pinknoise.Created,
'+00:00',
'+1:00'
),
'%l:%i %p'
) AS Created_formatted,
TIME_FORMAT(
SEC_TO_TIME(
TIMESTAMPDIFF(
SECOND,
pinknoise.Created,
CURRENT_TIMESTAMP() - INTERVAL '0' HOUR
)
),
'%Hh %im'
) AS elapsed,
tabA.CountRequests
FROM
pinknoise
INNER JOIN
(
SELECT
Count(*) AS 'CountRequests',
FirstName
FROM
`pinknoise`
GROUP BY
FirstName
) tabA
ON
pinknoise.FirstName = tabA.FirstName
WHERE
status = 'incoming'
ORDER BY
Created DESC

Answer 2

Your subselect is returning 2 values in the select portion where it only expects one value. I'm guessing you are getting the FirstName with the intent of doing a join. If so, then try this:
SELECT
p.id,
p.status,
p.FirstName,
p.LastName,
p.Track,
p.KeyChange,
p.Version,
DATE_FORMAT(CONVERT_TZ(p.Created,'+00:00','+1:00'), '%l:%i %p') AS Created_formatted,
TIME_FORMAT(SEC_TO_TIME(TIMESTAMPDIFF(SECOND, p.Created, CURRENT_TIMESTAMP() - INTERVAL '0' HOUR)),'%Hh %im') AS elapsed,
cnt.CountRequests
FROM
pinknoise p
inner join (SELECT p.FirstName, Count(*) AS CountRequests FROM pinknoise p GROUP by p.FirstName) cnt on p.FirstName = cnt.FirstName
WHERE
p.status = 'incoming'
ORDER BY
p.Created DESC;