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

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4
votes
1answer
145 views

Fast alternative for “NOT IN”

I have a table A that got a field called id that is the primary key of this table. I also have a table called B which also have a field called id as primary key. Now I want to get all rows from ...
4
votes
1answer
296 views

How to optimize: having COUNT(*)>1

Without considering the indexes, Is there a way to re-write this query and get the same result quicker? select fo.OrderNo, fo.OrderItemSeqNo, COUNT(*) from Facts.FactBackOrder fo group by fo.OrderNo, ...
4
votes
1answer
993 views

Oracle: How to gather stats in a logical standby database?

I have a Primary and a (logical) Standby Database. The Schema 'APP' gets synced. Now a User has performance issues running a query against some tables in this 'APP' schema of the Standby Database. On ...
4
votes
1answer
166 views

In SQL Server, what are the typical symptoms of parameter sniffing?

There is a wealth of information on the DBA.SE about what parameter sniffing is and how it relates to individual query performance circumstances. I was hoping that someone could provide some sort of ...
4
votes
1answer
226 views

Same Query takes 0 seconds on Server A, 7.5 minutes on Server B (same db/hardware/config)

I have a query (sql below) that is nearly instantaneous on 1 server, but takes 7.5 minutes on another virtually (key point) identical server. The estimated query execution plans have one obvious ...
4
votes
1answer
140 views

help required with indexing and query optimzation

After browsing most of the posts and after running out for options I am posting here. I have a table with 76,222,954 (76M) rows. It collects web site traffic based on country. Here is my table ...
4
votes
1answer
1k views

MySQL 5.5.8 InnoDB Foreign Key, JOIN performance

We are using aws/rds, MySQL 5.5.8. all InnoDB. For performance purposes, we have merged some data-elements into varchar fields; mini-sized int and date type fields; added covering indexes; ...
4
votes
0answers
649 views

SQL server query is slow *without* including execution plan [closed]

I have just set up fresh installation of SQL Server 2012 on a new server and I'm experiencing very strange performance problems. Long story short, for some reason not including execution plan makes my ...
3
votes
1answer
484 views

Improving select query

I was at an interview for a new job today and got asked a question regarding a SELECT query: SELECT lastname FROM users WHERE name='John'; This SELECT query is to run over a million rows. I was ...
3
votes
2answers
275 views

How can I eliminate this costly index seek operation from my query?

I have two tables in Sql Server 2008 that look something like this: Transaction_Details: Dataset, Department, Charge_ID, Transaction_Type, dos_month, post_month, amount ...
3
votes
2answers
5k views

Get table name from union query?

This is my query SELECT Id, productName, Largeimagepath, Discount, Price, Image FROM tablename1 where Active =1 union SELECT Id, productName, Largeimagepath, Discount, Price, Image FROM tablename2 ...
3
votes
3answers
477 views

selecting multiple instances of a record based on record lifespan over years

I have a table of items that have a origin date and a life span. I want to create a procedure that selects all of the items that will need to be replaced in a specific duration. I feel like there is a ...
3
votes
1answer
642 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 ...
3
votes
1answer
76 views

Optimal design for a large database

Brand new to databases, using postgresql on linux. I've done a decent amount of reading on the issue and looked through similar questions on here, but just want to confirm the most efficient way of ...
3
votes
2answers
964 views

Use a view to join tables or a stored procedure for a better execution plan?

First let me state I am a C# developer, not a SQL Server DBA, so please excuse my ignorance on SQL Server database query execution plans. What I want to know is for a stored procedure which the ...
3
votes
4answers
2k views

Finding all date ranges that overlap a target date range

Say I wish to store when staff are on holiday (FromDate, ToDate) and then I wish to find all staff that are on holiday between two given dates (QFromDate, QToDate). Now assume that I have many such ...
3
votes
3answers
281 views

Optimizing a query which runs through all hours in a day

I need help optimizing a query. I'm using PostgreSQL 9.3.4 currently but can upgrade to 9.4 if needed. I have a table with 60+ millions of records which looks like this: ...
3
votes
1answer
237 views

Why does SqlSentry Plan Explorer not give the duration of my queries?

I have a large nasty stored procedure in a 13gig database that takes 45 minutes to run when I include the actual execution plan. I save the query plan from SSMS and open in up in SQL Sentry Plan ...
3
votes
1answer
314 views

which one is more efficient query?

I have a table called STUDENT +-----------+-----------+-----------+---------------+ | StudentID | FirstName | LastName | EnrollmenDate | +-----------+-----------+-----------+---------------+ | ...
3
votes
2answers
1k views

How does compound index help speed up query?

Say we have a bunch of column in mysql table. Latitude Longitude Say we make an index (Latitude and Longitude) Well, the index will sort by Latitude first and IF the Latitude is the same it'll sort ...
3
votes
2answers
5k views

Will altering order of columns in GROUP BY affect performance?

I have a SQL query like this: SELECT A, B, (CASE WHEN C=0 THEN 0 ELSE 1 END), COUNT(D) FROM SomeTable GROUP BY A, B, (CASE WHEN C=0 THEN 0 ELSE 1 END) On a huge dataset the actual execution plan ...
3
votes
2answers
779 views

How do I count rows with two properties in one index scan in SQL?

I have a table Units where I have rows ItemId, ItemCreationDate, ItemUnitsCount. ItemId is a primary key and I have a clustered index over it. I need to output the following: for each day I need to ...
3
votes
1answer
55 views

Query Plan Error

I have an interesting situation. I use SQL2014 Enterprise version with SP1. The following query results an error message : The query processor ran out of internal resources and could not produce ...
3
votes
2answers
56 views

What's the best way to diagram this “relation” looking for performance and|or disk space savings

I am working in a DB diagram and I have a table called cm_identifier_type. Each record of this table can have or not a downloadable file (saved a file path). I have identified two possibles ways to ...
3
votes
2answers
55 views

Is it a better idea (performance is key) to store in a normalized table and retrieve by JOIN or in a single nvarchar column and retrieve using LIKE?

NOTE: The application is not really about websites or keywords, I am using that here only to provide reference points for discussion. I have a data set that is really just a string of words. Think of ...
3
votes
2answers
5k views

Dramatic decrease in SQL Azure performance after scaling to new edition

Yesterday, we scaled one of our databases in Azure from the old Business edition to the new Standard one (S2). Since then, it has been behaving rather erratically. We have a relatively simple table ...
3
votes
3answers
233 views

Change table scan in query plan to seek

I have an ORM generated query (Django) running against a local Postgres 9.1.11 instance that looks up ~5 records from two specific match fields. Due to the nature of the EDI load program, I need to ...
3
votes
2answers
941 views

UPDATE query with JOIN taking forever

I'm not very good with databases so please keep in mind even if the solution sounds like something everyone would have already tried, please post it because I likely have not tried it and it would ...
3
votes
3answers
150 views

How can I improve this query?

About a year back I introduced a query which returns a sort of "Customers Also Purchased" data-set. At the time it ran reasonably fast however, as of late it's become very slow, sometimes taking up to ...
3
votes
2answers
74 views

Need help improving sql query performance

I have this table: CREATE TABLE `property_ads_history` ( `id` int(10) unsigned NOT NULL AUTO_INCREMENT, `property_ad_id` int(10) unsigned NOT NULL, `advertiser_type` varchar(255) COLLATE ...
3
votes
1answer
78 views

Workaround for the limit of the number of missing indexes suggested by SQL Server's DMVs

In production, each instance of SQL Server has over 250 databases (what we call 'OrgDb's). The project I'm currently working on, aims to send all the reported missing indexes by SQL Server's DMVs to ...
3
votes
1answer
163 views

Do WHERE IN queries reindex the table after each set within the query?

I have a basic WHERE IN query that takes too long (30+ secs) to process. DELETE FROM `table1` WHERE ( djID, localID ) IN (("128","26"),("110","32")) The table I'm querying on has about 20 million ...
3
votes
1answer
88 views

Do fixed-width rows improve PostgreSQL read performance?

I have a table articles: Table "articles" Column | Type | Modifiers | ...
3
votes
2answers
507 views

Slow fulltext search due to wildly innacurate row estimates

Fulltext queries against this database (storing RT tickets) seem to be taking a very long time to execute. The attachments table (containing the fulltext data) is about 15GB. The database schema is ...
3
votes
2answers
29k views

Why can't we access SQL Server when a long query is running in Management Studio?

We have a SQL Server Database (2012 Standard edition). The database is accessed through an ASP.Net web page which displays the count of databases in different tables on page load. This work fine ...
3
votes
2answers
61 views

Why is MySQL ignoring my indexes?

I have a query select distinct id from patient where company_id in (1) and (name_last like 'peter%' or name_first like 'peter%' or remote_id like 'peter%') running on a table that looks like this ...
3
votes
1answer
1k views

How to get query runtime in PL/pgSQL to be as fast as console query runtime?

Basically I want to assign the result of a query to a custom type attribute. However I noticed that querying directly from the PostgreSQL console was about 0.071 ms and inside the function was 0.400 ...
3
votes
2answers
873 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 ...
3
votes
2answers
1k 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 ...
3
votes
3answers
2k 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 ...
3
votes
1answer
1k views

Query taking long on table with low record count

I have an Oracle flat table that grew to just below 800MB. The table was truncated and new records are being inserted. Currently there are <40 records in the table but a select * takes >30secs. ...
3
votes
5answers
708 views

Query optimization [Oracle]

The Query: select JOIN_RESULT.batch_id as BATCH_ID, JOIN_RESULT.unique_doc_id as DOCUMENT_ID, JOIN_RESULT.brand as BRAND, JOIN_RESULT.message_date_time as UPLOAD_DATE, ...
3
votes
3answers
2k views

Speed up search across multiple columns

We have a table: user_info (user_id,domain_id,first_name,middle_name,last_name,work_place,.,.,.) Now, we have a user search that search across three columns first_name,last_name and work_place. ...
3
votes
4answers
2k views

Optimize Query with Derived Table

I have the following query select ps.id, ps.title , IFNULL(s.likes,0) as num_likes , IFNULL(s.comments,0) as num_comments , IFNULL(s.ratings,0) as num_ratings , IFNULL(s.views,0) as num_views , ...
3
votes
2answers
76 views

Better understand table indexing best practices

I'm not completely sure when would I start indexing my tables, when there are some criterias that I should consider: The tables are not that big, I think (1000 - 10,000 rows). The searches are made ...
3
votes
1answer
91 views

Update multiple Ids when SET = (Sql Query)

I want to update multiple records however the value being set is based on the primary key of the given record. This is not an issue with a single record as I can use: UPDATE T1 SET A1 = (SELECT ...
3
votes
2answers
221 views

Any SQL where clause performance similar to where 1=0

(i'm using SQL Server 2008R2 or later) For centralize manage and consistent, there is a view definition as follow: CREATE VIEW view_all_situation ( select null as src, tf.col1, sum(col2) as fee, ...
3
votes
2answers
1k views

How to speed up select distinct?

I have a simple select distinct on some time series data: SELECT DISTINCT user_id FROM events WHERE project_id = 6 AND time > '2015-01-11 8:00:00' AND time < '2015-02-10 8:00:00'; And it ...
3
votes
1answer
1k views

How to optimise window queries in postgres

I have the following table with approximately 175k records: Column | Type | Modifiers ...
3
votes
1answer
3k views

Is it possible to avoid filesort?

Is it possible to avoid 'Using temporary' and 'Using filesort' for the following SELECT query? I can't figure out a way to do it. I tried adding indexes, for both top_expire and program, but didn't ...