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

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181 views

SQL Server 2008 search joining query

I have two table as one is the message table and another one is messageUser table. Now i need to check before insert a new row. for example, M_MessageMessageId========= ...
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479 views

SOLVED: Postgres 8.4.5: Bad query plan vs Good query plan when changing date range on large data table

SOLVED. I was able to resolve this issue by altering the time.date column to allow 1000 stats: ALTER TABLE time ALTER COLUMN date SET STATISTICS 1000; Now the queries are running very fast, down to ...
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208 views

How can I use mongoDB efficiently in this scenario?

I'm trying to build a system of documents that have hundreds of tags assigned to them, but each document-tag association has a certain condition it has to also meet so the document would be returned: ...
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1answer
284 views

mysql freeze/crash on JOIN

here is query: SELECT nw.news_id, nw.title, nw.description, nw.url, nw.date, nw.image, nw.status, src.title as src_title, src.keyword as src_keyword, src.url as src_url, src.icon as ...
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1answer
472 views

Optimizing User Defined Custom Columns

I am building a web based app that has the potential to have very high traffic and collect a lot of data. Most of this traffic will be utilizing the database. Database is MySQL InnoDB. I want to give ...
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2answers
1k views

Slow mysql fulltext query

I have a little problem with the performance of a mysql-query which uses a fulltext index. The following query SELECT Mention.id FROM mentions AS Mention WHERE (MATCH (`Mention`.`title_text`, ...
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188 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 ...
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410 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: ...
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131 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 ...
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4answers
636 views

Can migration from MS Access to SQL Server or … make database faster? [closed]

A company asked me to migrate their database from MS Access to SQL Server or MySQL because they think that on those engines their database will run faster. But I wonder if their problem isn't because ...
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97 views

Can I improve this query?

SELECT * FROM SameLogTable WHERE ID_Table IN (SELECT ID_Table-1 FROM SameLogTable WHERE <SameCondition>) OR ID_Table IN (SELECT ID_Table ...
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90 views

How can I replace the following query with ISNULL function in SQL?

I have the following query. For performance optimization reasons I have been asked to replace the logic with ISNULL function in SQL. How can I achieve this? please advice. SELECT ...
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4answers
94 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 ...
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2answers
436 views

Tsql Query speed slow due to Or within where clause, causing index scan instead of seek

I have been working on making this query work more efficiently. I found that the number of Ors within the where clause are the biggest problem within this query. This query sits in a stored ...
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2answers
232 views

Database SQL Script very, very slow (string manipulation over 700k rows)

I have table containing 700,000 rows containing a string id field with values such as rec-232276-dup-0 and rec-354240-org. The rec- is constant but the other parts of the id can change. I want to ...
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3answers
5k views

Will more indexes on a table affect performance? [duplicate]

Possible Duplicate: How do indices impact query performance? How to know when/if I have too many indexes? Say ‘X’ report using some "where" condition in the statement so we are creating ...
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2answers
68 views

Oracle query optimization

We have a query that runs on a view and its execution time is about 6 min. SELECT COUNT(*) FROM someschema.item_total_violations WHERE channel_id = 122507833 AND item_date >= ...
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2answers
804 views

Why would a long running query remain sleeping and with null wait_info

The following query was run on SQL Server 2008 R2 and took over 1 hour to run: select log_id, type, instance_id from ts_cache_log where log_id > 146400 order by log_id It produced 0 rows ...
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1answer
68 views

Similar hardware, Same DBconfiguration and Database but different status variables result between Windows and Linux server [closed]

I have two database servers - one is Windows - 2008 and another is RHEL5 with similar hardware configuration. Both OS are 64 bit. MySQL 5.1.58 community edition is installed on Windows servers while ...
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2answers
60 views

Which one is better way to insert data? [closed]

I have two cases case create proc createEmployee @firstName varchar(255), @lastName varchar(255) = null as insert into Employee_Tbl values (@firstName, @lastName) case create proc ...
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2answers
72 views

A simple database and Query System? [closed]

I am new to databases and trying to solve one problem in which I have to build a simple database having few entries and then querying that database and then recording that answers from the database. I ...
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2answers
1k 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, ...
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3answers
2k 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 ...
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2answers
847 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' ...
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1answer
130 views

Similar queries taking different times to complete

I had the following query: SELECT nvl(sum(adjust1),0) FROM ( SELECT ManyOperationsOnFieldX adjust1, a, b, c, d, e FROM ( SELECT a, b, c, d, e, SubStr(balance, ...
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1answer
26 views

Clustering a heap by date in stead of unique composite key

I've been working on improving the performance of a large reporting database. This database is 2TB in size, and one of the larger tables is a heap with three non-clustered indexes on it. The ...
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2answers
64 views

Does it make sense to order condition in where query?

We have a clustered index in table Tbl with order of A,B,C. Does it make senses to write a query to have WHERE A = @a, B = @b, C = @c or it'll be as same as WHERE C = @c, B = @b, A = @a Does the ...
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3answers
73 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) ...
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2answers
64 views

MySQL query optimization for legacy application

I'm working with a legacy application that started out with little data years ago (developed by a third party custom for this client), and now we're seeing MySQL load skyrocket on this query alone. ...
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1answer
465 views

Take query results and insert into new table [closed]

So I have the following query: DECLARE @tbl TABLE(value int) *--The same function but with the number of the random numbers ;WITH Nbrs (n) AS ( SELECT 1 UNION ALL SELECT 1 + n FROM ...
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2answers
892 views

How can I speed up this query on table with 65 million records

select hash_id, hash_value, substring(T.cri, 1, 7), substring(T.cri, 9, D2.Pos-9), substring(T.cri, D2.Pos + 1, D3.Pos - D2.Pos - 1), ...
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1answer
812 views

Calculating time spent on query cache lock

How can I calculate the total time my MySQL database is spending Waiting for query cache lock ? I've found two specific very simple tables that adding a SQL_NO_CACHE drastically improved the ...
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2answers
92 views

Query performance differs greatly between a development setup and production

I'll try to keep this question straightforward, though I am dealing with a big ball of mud. When I run my test query acrossed linked servers both located locally (on a shared virtual host), the ...
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1answer
1k views

Optimizing ORDER BY for simple MySQL query

I'm trying to optimize this really simple query, and it gives me grief for a day now :( Seems pretty straightforward, I need to select with a JOIN from 2 tables, and get top X results sorted in a ...
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1answer
332 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 ...
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1answer
45 views

improve long running query

I have this query INSERT INTO interactions( user_id, external_object_id, origin, interaction_type, interaction_sub_type, published_at, origin_id, created_at, updated_at) SELECT ...
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1answer
55 views

Optimizing key lookup in subquery with UNION ALL

I am trying to optimize following query (little bit more complex actually, but this is important part): SELECT Id, StatusDate, [...Lot Of Columns...] FROM ( ( SELECT Id, StatusDate, [...Lot ...
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2answers
51 views

SQL Server 2005 query with multiple conditions, some indexed, some not

I have a table with 50 million rows. It is indexed on zip. A query Select * from table where zip = '12345' returns 20,000 rows in about 2 seconds When I add an additional condition it jumps to ...
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86 views

Viewing execution plans for queries with parameters

I have a sample query generated by an application (Microsoft Dynamics AX 2012 in this case) which is ineffective performance-wise (cross joins, order by etc.) I would like to display its execution ...
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1answer
88 views

What is the best query to get the latest row version based on time?

I'm wondering what can be the most efficient query to get the latest rows from the following table. CREATE TABLE AGE_DATA ( INSERTED_DAY TIMESTAMP(6), HOSTNAME VARCHAR2(255 CHAR), CONCEPT ...
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4answers
101 views

Why does this query take 32 sec to execute?

I keep my history records in one table and my pertinent data in another. I want to grab only the files from myfiles that currently have a given status recorded in statuses (ie, the latest status is ...
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2answers
81 views

Querying MySQL, duration increases 10x fold after adding one more Join

I have a somewhat complicated query consisting of many joins on an issue tracker/project management database in MySQL. My issue is that my query was doing OK while I was in the process of building it ...
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1answer
75 views

Simplifying query by adding Computed Column, performance impact?

The dev team came across the following query (might be incomplete; it's retyped from a screenshot) which had caused slowness: SELECT d.catalogno, d.itemid, SUM(lineamount+taxamount) AS Amount, ...
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1answer
72 views

How can I control the order of a query regarding to inner join

I have 3 tables. They have table_a 5m records table_b 20m records table_c 20m records I'm performing the query below. SELECT * FROM table_a a INNER JOIN table_b b ON a.a_id = b.a_id AND ...
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1answer
442 views

Best way to store country and city information

I always wondered what is more efficient between two. There is one "main" table where I store all user related informations. Also, there are two more tables, country and city tables. city table ...
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1answer
63 views

How can I write queries as fast as possible in MySQL? [closed]

I'm looking for two things: Awesome manual about writing fast MySQL queries. Tool which will decompose my query into discrete steps, and give estimations of each step. I've seen the next tool, ...
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2answers
2k views

How to fix slow LIMIT queries with big offsets without heavily rewriting them?

Imagine a very basic example of your average discussion board. For example: CREATE TABLE threads ( id INT UNSIGNED NOT NULL AUTO_INCREMENT, title VARCHAR(100), PRIMARY KEY (id) ) CREATE ...
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2answers
117 views

Get only future records

I have the following query: SELECT master.master_id, master.showname, MIN(CONCAT(shows.show_date, ' ', shows.show_time)) AS first_show_date, MAX(CONCAT(shows.show_date, ' ', shows.show_time)) AS ...
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2answers
306 views

What is the performance difference between IN (42) and id = 42 in MySQL?

Are there any performance differences between SELECT * FROM table WHERE id IN (42); and SELECT * FROM table WHERE id = 42; ? The question is about just supplying a single value. The ...
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1answer
275 views

Improve Insert performance for 200 Million rows

How can the following insert statement be improved - which varies from 20mins on certain days to 70-140mins on most other days. SELECT DISTINCT od.SourceID, od.OrderID, od.OrderLineNo, ...