0
votes
0answers
85 views

Slow query with ORDER BY with index created (more than 4mins on 0.6million records

I ran into a very weird query performance situation. If I run this query without order by, it finish in millsecs, with order by, it ends up with more than 4mins. EXPLAIN SELECT `book_book`.`id`, ...
2
votes
2answers
836 views

MySQL not using indexes when joining against another table

I have two tables, the first table contains all articles / blog posts within a CMS. Some of these articles may also appear in a magazine, in which case they have a foreign key relationship with ...
0
votes
1answer
252 views

Postgresql table with one integer column, sorted index, with duplicate primary key

I want to have a table in PostgreSQL with these properties: One column with an integer Allow duplicates in this column. Duplicates will be rare. Duplicates have no meaning logically and will be ...
1
vote
4answers
298 views

MySql Order by isnull() Performance Problem

my sql below is use for listing stock added from 10 days ago. Order by isnull(Price) is use so that stock without any price yet will still being listed. AddDate and Price has an index. SELECT Id, ...
0
votes
1answer
329 views

Mysql: order by field or select union?

As a newbie, I expected Mysql to return the rows of this query ordered by their ids order in the id clause select * from test where id in (3,1,2) Unfortunatelly for me, that's not true. The results ...
9
votes
1answer
4k views

Order by column should have index or not?

I have added indexes to table which are used for searching result. I am showing results by ASC or DESC order. So that column should have index or not? I have 2 more indexes on that table. How ...
3
votes
3answers
967 views

Does ORDER BY on a clustered key effect performance?

Say I have a table clustered on PrimaryKey, and in all cases I want my results to be ordered by PrimaryKey so I additionally always ORDER BY PrimaryKey in all queries. Does this ORDER BY affect ...