Questions tagged [query-performance]

Use this tag for questions about improving the performance and/or efficiency of database queries.

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7
votes
2answers
16k views

Why won't SQL Server optimize the UNIONs?

Consider these queries (SQL Fiddle): Query 1: SELECT * INTO #TMP1 FROM Foo UNION SELECT * FROM Boo UNION SELECT * FROM Koo; Query 2: SELECT * INTO #TMP2 FROM Foo UNION SELECT * FROM Boo UNION ALL ...
4
votes
3answers
12k views

Duration Field in Profiler

I would like to monitor the script which takes more than 25 Sec. When i use filter i am not able to see the duration taken by the script. How can we get the time taken to execute the query. My ...
1
vote
1answer
621 views

Retrieving data speed tweaks SQL Server 2005

I have a database in Microsoft SQL Server 2005. I have table with 3 columns, namely HASHKEY (BIGINT), NOTE_ID (INT) and TIME_OFFSET (INT). Columns HASHKEY has 19 digit BIGINT values, which can ...
1
vote
1answer
464 views

MySQL Query Optimization - Indexes & Joins 12 million+ records

I'm running the following query: SELECT `track_title`.`title`, `track`.`id`, `artist`.`name` artist, `album`.`title` album, `st_tag`.`tag`, `track`.`year` FROM `track` ...
0
votes
2answers
3k views

how to find similar word with more similarities

how to Find words with length less than or equal... declare @inp nvarchar(max),@data nvarchar(max) set @inp='You can dance, you can jive, having .... jove... jve, ...' set @data = 'jeve' ...
1
vote
0answers
646 views

Sql Execution Plan - Hash Match

I'm currently working on a Sql Query that's having performance issues. I ran the execution plan and saw the Hash Match has 50% cost and also, doing a index scan. I'm starting to learning about the ...
1
vote
1answer
737 views

MySQL query optimization with aggregate ORDER BY

I have an analytics table that stores metrics aggregated the day level. I need to ask questions such as "For a given date range and client, what are the most popular items." The schema is as follows: ...
3
votes
1answer
209 views

MySQL table architecture

Background information: I have a table containing upload information, every day I get more and more uploads but most of the queries I run center around information gathered within the last 12 months; ...
0
votes
1answer
2k views

How to measure a perfomance of SQL Server database? [closed]

I have the task to improve the performance of a SQL Server 2012 database (one of 4 in an instance) by 60% confirmed by corresponding statistics. So, I need to measure "performance" of the RDBMS ...
0
votes
1answer
637 views

Can I speed up this slow query which should be limited by MIN/MAX values?

The intention here is to look at the user retention over a period of time. My current solution employs a temporary table, since I do this over several ranges. CREATE TEMPORARY TABLE ...
0
votes
1answer
245 views

Using an enum index to limit records

A common issue, just not sure on the keywords. I have a table of assessments (14k+ records). Each assessment can be in many different states ('draft', 'proofing', 'amends', etc... and 'done'). Most ...
3
votes
1answer
802 views

SQL Server WHERE clause on CLR method (spatial) peformance

I have a query that joins to a table containing 2 million rows and need to filter on its geometry column by its geometry type (using geom.STGeometryType()). The query takes less than a second to run ...
2
votes
3answers
13k views

Simple select is taking too long

I am facing an issue with the performance. The selection of data from table is taking more than 20 sec to retrieve close to 300k records. Created a clustered index on col1 and col2 but no improvement. ...
2
votes
1answer
948 views

SQL Server 2005 - Query optimization for fetching large number of rows from table with 750 million rows

Brief on application: This is audio fingerprinting application, being developed in Java with Microsoft SQL Server 2005 database. I have one application to create fingerprints of original songs and ...
4
votes
5answers
2k views

How can I prove that the following T-SQL is bad for performance?

I have recently inherited a codebase with a large amount of Stored Procedures. The system they are supporting is encountering numerous performance problems which I am looking in to. A number of the ...
1
vote
1answer
62 views

What ways are there to limit the processor / ram requirements of a specific query?

Every once in a while, I need to run some very expensive query on a production server. Think spaghetti joins. This is likely to affect the server operation, and I don't want that. What ways are there ...
1
vote
1answer
1k views

MySQL looking up more rows than needed (indexing issue)

In our MySQL 5.5 database, we have following InnoDB table with 30M+ rows: +----------------+-------------+-----------------+--------+ | participant_id | question_id | given_answer_id | status | +-----...
1
vote
1answer
86 views

Does limit impact affected rows or not?

I have this table: CREATE TABLE IF NOT EXISTS `usergroups` ( `id` int(11) unsigned NOT NULL AUTO_INCREMENT, `user_id` int(11) unsigned NOT NULL, `group_id` smallint(5) unsigned NOT ...
4
votes
2answers
2k views

Efficiently query MAX over multiple ranges

When performing a MIN() or MAX() over a single range covered by an appropriately sorted index, SQL Server does a TOP() and so returns the value after fetching just one row. When the search criteria ...
1
vote
0answers
265 views

Mysql performance issue when selecting text column

I have a performance problem when selecting rows containing text fields: SELECT id FROM message WHERE NOT(message.sender_id = 368352 AND message.is_deleted_sender = 1) AND NOT(message....
1
vote
1answer
319 views

T-SQL Gurus, I need help optimising these queries for performance

I would like to have suggestions on improving the performance of some queries. These will be run on SQL Server 2008 R2 against a single table called dbo.bids In a production environment the table ...
4
votes
1answer
819 views

performance issue caused by IO?

Just curious to get an issue sanity checked . . . I'm trying to ascertain whether a performance issue experienced by users is the result of the app, server it sits on or SQL Server. Looking at ...
3
votes
1answer
272 views

Optimizing complex join predicates [closed]

Table Definitions CREATE TABLE [dbo].[Pin_Mtg] ( [MtgId] bigint NULL, [CntyCd] char(5) NOT NULL, [BatchDt] int NOT NULL, [BatchSeq] int NOT NULL, [MtgSeq] tinyint NOT NULL, [...
1
vote
1answer
89 views

Query for View with unique entries from Database with repeated entries

I have a table with columns of Hotel names, city name and country name (of the respective hotels). I need to create a view of unique entries which will contain city name and country name columns. Any ...
0
votes
2answers
123 views

Help creating this query

I'd like to integrate the following query: SELECT parent.id , COUNT(child.id) AS child_count FROM messages parent INNER JOIN messages child ON child.parent_id = parent.id ...
0
votes
2answers
523 views

Understanding multiple indexes with MySQL (and performance)

I have a "phones" table with around 120 000 records, it contains phone_id, phone_number, phone_user_name, phone_last_contacted, etc. The phone_id is index and looks like: 1,2,3,4 ... 120 000. But I ...
0
votes
1answer
50 views

Query Optimization for added value

I have a query that's behaving a bit oddly. In my database I have a table called "records". It tells me a bunch of information about what applications a user ran on my company's machines. I'm ...
1
vote
3answers
8k 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 create ...
0
votes
1answer
101 views

strange “using where” in simple query

I have a table with this structure: mysql> describe user_groups; +----------+----------------------+------+-----+---------+----------------+ | Field | Type | Null | Key | ...
1
vote
2answers
688 views

How to avoid timeouts during big DML operations

I have a big insert script I need to run. Its about 55,000 records and 160 columns. The script is already created and I can't create it again. The problem I have is that this runs for about 4 hours ...
1
vote
1answer
66 views

Condense Query Results with Wildcard

I have the following query: select programVersion, count(programVersion) from records R inner join Programs P on P.programID=R.usageProgramID where programName="word" ...
2
votes
2answers
969 views

Trigger update does not seem to finish

I'm new to PostgreSQL triggers & functions and such. I've got a table: keywords and each keyword should be unique. So when I try to insert a keyword that already exists, it should simply update ...
3
votes
2answers
544 views

Can I use a foreign key index as a shortcut to getting a row count in an INNODB table?

I have a table that has a large number of rows in it. The primary key (an auto-incrementing integer) is, by default, indexed. While waiting for a row count to be returned I did an EXPLAIN in another ...
15
votes
1answer
1k views

How does SQL Server know predicates are correlated?

While diagnosing SQL Server 2008 R2 queries with poor cardinality estimation (despite simple indexing, up-to-date statistics, etc.) and hence poor query plans, I found a perhaps-related KB article: ...
1
vote
1answer
444 views

Query tuning help needed (Hash Match and Table Scans) [closed]

I need help optimizing the following query (returning ~8k rows): SELECT A.sys_id, 'AppSvrRels' = CAST(SUBSTRING((SELECT (', ' + T.name) FROM ( ...
3
votes
1answer
8k 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
5k views

Speeding up MySQL NOT IN (Subquery) [duplicate]

I'm currently up to try to improve the performance of some of my queries. As far as I know, statements like "IN" or "NOT IN" are even faster with a large amount of values if a subquery on an indexed ...
0
votes
1answer
473 views

Database schema design help needed

I am developing a PHP application expecting millions of records both parent and children. My goal is to design an optimized database design to achieve high speed and performance. This application ...
1
vote
2answers
787 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 = members....
6
votes
3answers
3k views

MySQL optimization - year column grouping - using temporary table, filesort

I have a transactions table which is having 600,000 records, I need to list the count for the dashboard on financial year basis. The table used is MyISAM. I tried adding index for the transaction date ...
2
votes
4answers
26k views

How can I query data from a linked server, and pass it parameters to filter by?

I have a really big query that needs to be run on multiple databases, and the results appended to a temp table and returned. The basic syntax looks something like this: INSERT INTO #tmpTable (Id, ......
0
votes
1answer
129 views

How to optimize query?

I need to optimize the following query: SELECT DISTINCT column1, column2 FROM tbl_name WHERE column3 = 'x' AND TRIM(UPPER(column4)) = TRIM(UPPER('y')) AND TRIM(UPPER(column5)) = TRIM(...
1
vote
0answers
355 views

Mysql key_buffer_size already 16GB but some fulltext searches are still slow

I have a query w/ full text search which takes 5 - 10 secs. key_buffer_size is already 16GB. Table has 15 million records and has a compound fulltext index on fields: categories and company. Table ...
3
votes
2answers
2k views

Improve CTE performance

is there a way to improve the performance of a recursive CTE like below, I am unsure if I can add indexes on joins when the joins are using ROW_NUMBER? DECLARE @File_Name VARCHAR(8000), @Disk ...
5
votes
2answers
26k views

Get username and/or IP address responsible for a query

I use the following query to find performance improvements in queries: SELECT TOP 20 SUBSTRING(qt.text, (qs.statement_start_offset/2)+1, ((CASE qs.statement_end_offset WHEN -1 THEN ...
2
votes
1answer
2k views

Would adding indexes to my foreign keys improve performance on this MySQL query?

Consider the following query: SELECT `locations`.`id` AS `location_id`, `locations`.`address`, `locations`.`lat`, `locations`.`lng`, `tickets`.`status_id`, `customers`.`name`, `tickets`....
6
votes
1answer
7k views

How to properly index hstore tags column to faster search for keys

I imported a large area of OpenStreetMap's planet.osm file into a postgresql database. The database contains a table called nodes. Each node has a geometry column called geom and a hstore column ...
4
votes
1answer
443 views

What is the name of this type of query, and what is an efficient example?

The purpose is to find a parent, given it's children. For example, say you have a marketing package (aka a "combo"), and want to match it based on the products in it. Example table/data: create table ...
2
votes
2answers
362 views

Changing ORDER BY direction causes performance issue

I use MySQL 5.6, and I have two tables each with 16M rows: CREATE TABLE IF NOT EXISTS `newsstudios` ( `id` int(11) NOT NULL AUTO_INCREMENT, `title` varchar(255) COLLATE utf8_unicode_ci NOT NULL, ...
-1
votes
1answer
160 views

Query performance in SQL Server [closed]

What factors should I check when I compare the performance of a query? I saw many articles stating about IO cost, subtree cost (by using Execution plans), statistics such as CPU time, elapsed time (...