Tagged Questions

2
votes
1answer
62 views

Best practice: Unions or a derived table?

I've inherited a medium-sized database with a terrible schema. The sanitized portion in question is like so: CREATE TABLE `pending` ( ... `invoice` int(11) DEFAULT NULL, `lid` int(11) DEFAULT ...
2
votes
1answer
114 views

Selecting minimum value using a subquery

I need to write a query to grab the lowest price from each merchant and output the price link (p_link) and some other information such as merchant name + rating. We have a table for prices ...
1
vote
1answer
363 views

Select multiple columns in subquery

I am having trouble selecting all cloumns in a sub query and can't seem to get no where with joining for replacement. http://sqlfiddle.com/#!2/2481e/1 The link is to the schema with my current ...
3
votes
1answer
328 views

Subqueries run very fast individually, but when joined are very slow

ypercube solved the problem. Subqueries were totally unnecessary, and the whole thing works with plain joins. It is still strange that MySQL's optimizer could not make use of my original query, ...
0
votes
2answers
169 views

Tuning query to remove joins for reporting

This is the query I was sent. There is currently no data in the system as I was converting this query from teradata to SQL server. SELECT user_id FROM user_table LEFT OUTER JOIN ( SELECT user_id , ...
1
vote
1answer
124 views

Querying multiple tables

I am working on a query from our ticketing system, and I am having problems figuring out the best way to join these tables together. I have the following tables/fields: SR_service: stores ticket ...
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 ...