order, group and search query. too many selects - mysql

Question

i am running this query, witch consists of 3 recursive selects.
select idigorUserFields
from ( select *
from ( select *
from igorUserFields f
where f.idigorUsers = 1
order by f.idigorUserFields desc) tbl
group by tbl.idigorUserFieldTemplates ) tbl2
where value="qf" and idigorUserFields = 28
what I am trying to do is simple:
get all fields, order by insert date ( i am using primary key for that )
get the last inserted value for a field (idigorFieldTemplates)
compare the last inserted field with the one i am about to insert, to save some space on the database
some relevant info:
idigorUserFieldTemplates is the primary key for a "html user fields table"
the last inserted value is the one displayed on the program
also, I have a sqlfiddle! with some data to test.
my question is: can I make this query better? and what do I need to use to do that.

Answer 1

Alright so it looks like you want to get the last inserted value for a given user and value and then compare that with the data you are about to insert. Here's how I would tackle that
SELECT a.idigorUserFieldTemplates
FROM igorUserFields AS a
INNER JOIN (SELECT MAX(idigorUserFields) as max_id FROM igorUserFields WHERE idigorUsers = 1 AND value="qf") AS b
ON a.idigorUserFields= b.max_id
The subquery is giving me the largest idigorUserFields for which idigorUsers = 1 AND value="qf." For this to work, you have to assume that that the primary key (idigorUserFields) is incrementing with date. You indicated in your post that it does, so hopefully this assumption is okay.
Once we've got that last updated record, we then join back with igorUserFields to get the corresponding value of idigorUserFieldTemplates
edit:
I want to get the last inserted for a given user and field. then compare it with what i am about to insert.
I am sorry if I was not clear enough about what I wanted.
I modified the above sql and i got what i wanted:
SELECT a.* FROM igorUserFields
AS a INNER JOIN
(SELECT MAX(idigorUserFields) as max_id
FROM igorUserFields WHERE idigorUsers = 1 and idigorUserFieldTemplates =6) AS b
ON a.idigorUserFields= b.max_id
AND value="qf"
thanks! now I got a more efficient solution :)

Answer 2

if all you want is the largest id by specific data just specify that order it and limit it like so
SELECT idigorUserFields
FROM igorUserFields
WHERE idigorUsers = 1 AND value="qf"
ORDER BY idigorUserFields DESC
LIMIT 1
DEMO
if you are trying to get the last inserted value then you can get the largest idigorUserFields assuming its auto incremented.
SELECT MAX(idigorUserFields) FROM idigorUserFields
and then if you want a specific column from that field you could use it as a subquery
SELECT f.idigorUserFieldTemplates
FROM idigorUserFields f
WHERE f.idigorUserFields =
( SELECT MAX(idigorUserFields)
FROM idigorUserFields
WHERE idigorUsers = 1 AND value="qf"
)