Get value of mySQL query grouped by id - mysql

Question

I want to know an efficient way to solve the following query. Essentially I have the following two classes
CREATE TABLE `example`.`doc` (
`id` INT NOT NULL AUTO_INCREMENT,
`uuid` INT NOT NULL,
`creator` VARCHAR(32) NOT NULL,
PRIMARY KEY (`id`);
CREATE TABLE `example`.`pic` (
`id` INT NOT NULL AUTO_INCREMENT,
`docuuid` INT NOT NULL,
`taken_at` DATETIME DEFAULT CURRENT_TIMESTAMP,
`lat` DECIMAL(3,10),
`lon` DECIMAL(3,10),
PRIMARY KEY (`id`);
this two tables are related by uuid (I know this is not the best idea to link two tables, but the table is like this). uuid is unique per doc. With the following query
SELECT
`doc`.`id` AS `docId`,
`doc`.`uuid` AS `uuid`,
`doc`.`creator` AS `creator`,
COUNT(`pic`.`id`) AS `pics`,
MIN(`pic`.`taken_at`) AS `min_date`,
MAX(`pic`.`taken_at`) AS `max_date`
FROM
`doc` INNER JOIN
`pic` ON (`doc`.`uuid` = `pic`.`docuuid`)
WHERE (
`pic`.`docuuid` IS NOT NULL AND
`doc`.`uuid` IS NOT NULL)
GROUP BY `doc`.`uuid`
I get, for each doc, the date at witch the first and last pics was taken. Additionally I want to get in this query, for each doc, the latitude and longitude of the first and last pic taken at that doc.
For example, If I have
doc1 = (id=0, uuid=1)
doc2 = (id=1, uuid=2)
pic1 = (taken_at=2021-01-01, docuuid=1, lat=1, lon=2)
pic2 = (taken_at=2021-01-02, docuuid=1, lat=3, lon=4)
pic3 = (taken_at=2021-01-03, docuuid=2, lat=5, lon=6)
pic4 = (taken_at=2021-01-04, docuuid=2, lat=7, lon=8)
pic5 = (taken_at=2021-01-05, docuuid=2, lat=9, lon=10)
then I want to get for doc1 minLat=1, minLon=2, maxLat=3, maxLon=4 and for doc2 minLat=5, minLon=6, maxLat=9, maxLon=10

Answer 1

You mat continue by joining the results of your current query with the pics table and extracting the desired details of each pic, I've included a sample below:
SELECT
t.*,
earliest_pic.lat as minLat,
earliest_pic.lon as minLon,
latest_pic.lat as maxLat,
latest_pic.lon as maxLon
FROM
(
SELECT
`doc`.`id` AS `docId`,
`doc`.`uuid` AS `uuid`,
`doc`.`creator` AS `creator`,
COUNT(`pic`.`id`) AS `pics`,
MIN(`pic`.`taken_at`) AS `min_date`,
MAX(`pic`.`taken_at`) AS `max_date`
FROM
`doc` INNER JOIN
`pic` ON (`doc`.`uuid` = `pic`.`docuuid`)
GROUP BY `doc`.`uuid`
) AS t
INNER JOIN `pic` as earliest_pic ON earliest_pic.taken_at = t.min_date AND
earliest_pic.docuuid = t.docId
INNER JOIN `pic` as latest_pic ON latest_pic.taken_at = t.max_date AND
latest_pic.docuuid = t.docId
Let me know if this works for you