Tagged Questions
0
votes
2answers
56 views
How do I use subquery on the same table in MySQL?
I have a query like this which takes a really long time to run. The table is around 4 million rows.
DELETE FROM TABLE WHERE value_was IS NULL OR value_was <= value_now;
I'm hoping I could ...
1
vote
2answers
221 views
SELECTing multiple columns through a subquery
I am trying to SELECT 2 columns from the subquery in the following query, but unable to do so. Tried creating alias table, but still couldn't get them.
SELECT DISTINCT petid, userid,
(SELECT ...
2
votes
1answer
149 views
Does MySQL have problems with nested insert like with subqueries in where?
Query 1:
INSERT `personal`.`locations`
SELECT DISTINCT `s`.*
FROM `references` `t`
JOIN `locations` `s` ON `first_id` = `s`.`id`
WHERE
`lat` >= 37.3
AND `lat` <= ...
-3
votes
2answers
268 views
Optimisation sub query SQL Server
I would like to optimise the query below because it's actually taking 40% of the time in the real one. I HAVE to get the first line in the table 2 for each line in the table 1. The relationship is 1 ...
3
votes
1answer
2k views
mySQL query optimisation — multiple joins or select … where not in (select distinct…)?
Background
I have a Drupal install accessing a large users database (~200k rows) and my "People finder" functionality needs to access all those rows (in a random order). I don't seem to be able to ...
3
votes
1answer
2k views
Query performance with subquery and IN clause
I am trying to select a range of data for multiple devices (unique serial numbers) from a historical table and was wondering why there is such a big difference in time for the following queries:
...
