A class of issues where a database executes a query inefficiently due to the optimiser selecting an innapropriate query plan.

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2
votes
2answers
93 views

Joining two Mysql VIEWs takes a very long time

I have a textbox (for which I used jQuery auto-completion) in my PHP form where user can insert an actor/actress name and then by clicking "Search" button, a new window is opened showing list of ...
2
votes
1answer
189 views

Postgres Performance Over Group by with MAX and MIN

I just want to retrieve the data for specific location of customers with their ever first and last purchases made in the system. Table details : CREATE TABLE customer_location ( id UUID, location_id ...
2
votes
1answer
228 views

Getting each status change in a table

I have a table that holds status changes per item. The item can go in and out of a status multiple times. ItemTable (ItemId int, Status varchar(50), DateOfChange date) I need to pull the date of ...
2
votes
1answer
490 views

T-SQL Query runs quickly on local PC, but slow on SQL Server?

I have a query with a few joins and a couple of basic SUM(...) statements, and no parameters. It's been running without issue for months - but has suddenly started running very slowly on the server ...
2
votes
2answers
118 views

Convert to Self JOIN

I have a correlated sub query, which is taking 16 Minutes to execute. How can I convert it to join or optimize it. SELECT SSF.SM_StockCode, SSF.ST_ItemSize FROM Stock AS SSF WHERE ...
2
votes
1answer
2k views

Query taking non-consistent time to execute [closed]

I have a query which takes large time to execute sometimes.When i checked the speed it was taking 15 seconds.But actually it should run faster than that.When i again checked the query it again ...
2
votes
1answer
131 views

How to know what to investigate and how for a VERY slow stored procedure

I have inherited a large and slow stored procedure and it's giving me a nightmare: I'm not a DBA, although I have some knowledge, but I don't know where to start to identify this bottleneck. I have ...
2
votes
3answers
273 views

How to get all non deleted messages from one user

I have two tables one for messages called default_messages and the other for recipients called default_recipient. This is how SQL for those table looks like: CREATE TABLE IF NOT EXISTS ...
1
vote
1answer
586 views

MySQL SUM with multiple GROUP BY on same table

What is the best way to produce several sum results based on different group by conditions on the same table in MySQL? I believe I'm doing a bad select, but I can't figure out a better way. Imagine ...
1
vote
2answers
655 views

Improving `GROUP BY` query performance in sqlite3

I have a little web-application that is using sqlite3 as it's DB (the db is fairly small). Right now, I am generating some content to display using the following query: SELECT dbId, dlState, ...
1
vote
2answers
57 views

MySQL query performance question

I have a MySQL database where I would like to return results based on multiple rows. id | key | value | selector --------------------------------------------------------- 1 | username ...
1
vote
1answer
97 views

Slow queries InnoDB occasionaly

I have the next table: CREATE TABLE `sessions` ( `session_id` char(32) COLLATE utf8_unicode_ci NOT NULL, `session_expires` int(11) NOT NULL DEFAULT '0', `session_data` varchar(10000) COLLATE ...
1
vote
1answer
173 views

Is there any way to get the estimate cost of executing a query in MySQL?

In PostgreSQL, EXPLAIN or EXPLAIN ANALYZE will show the estimate cost of executing a query. But EXPLAIN in MySQL doesn't provide this information. How can I get the estimate cost without installation ...
1
vote
2answers
73 views

Need some support on MySQL Query

I have a query SELECT leads.id, sfav.id is_favorite FROM leads INNER JOIN teams tst ON tst.team_set_id = leads.team_set_id INNER JOIN members members ON tst.team_id = ...
1
vote
1answer
121 views

Several values from different tables

I'm totally lost here and not know how to get this to work and hope any can help me here. I have several tables: default_users, default_profiles, default_status, default_comment and latest ...
1
vote
0answers
177 views

Get all comment.message, status.message, users.* and profiles.* where users.user_id exists in friend.friend_id or friend.user_id

I need some help building this query because it's a bit complicated at least for me. I need to get all comment.message, status.message, users.* and profiles.* where users.user_id exists in ...
0
votes
4answers
53 views

Single SQL query to retrieve data in a particular order (not ASC/DESC)

I have a MySQL table, let's say called reviews review_id, product_id, language_id, rating, review, author language_id ranges from 1 to 10 for 10 different languages. Let's say I determine that my ...
0
votes
1answer
66 views

Skewed Clustered Index

I have a SQL Server database that has a pretty important table (join wise) that contains just over 2.1 million rows. For the VARCHAR column that defines the clustered index, 17.5k rows contain unique ...
0
votes
3answers
70 views

How to return last used record?

I have simple table called ips with 2 field ip and address, which schema is following CREATE TABLE IF NOT EXISTS `ips` ( `id` int(10) unsigned NOT NULL AUTO_INCREMENT, `address` varchar(255) ...
0
votes
2answers
686 views

How to get rid of using temporary when using DISTINCT in MySQL?

When I do the following, I get Using where; Using index; Using temporary. How do I get rid of Using temporary? http://sqlfiddle.com/#!8/f61a2/3/0 CREATE TABLE `test` ( `a` varchar(45) NOT NULL, ...
0
votes
1answer
420 views

optimize big sql query

My query has to return a statistics for example for march containing productname and price and its sidedishes (1:n relation) with the right price of each sidedish and the right tax for each sidedish ...