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

learn more… | top users | synonyms

0
votes
0answers
18 views

Forked database doesn't use same query plan as original even after Vacuum Analyze

I forked a production database for some testing. I'm running a query select distinct store_id from <table>, where there is an index on "store_id" (the index was created via create index ...
1
vote
1answer
38 views

Order by varchar mysql

Is there anyother alternative for order by varchar clause? At worst case consider I want to order by varchar column that is not indexed. When I tested a query with loads of data it took many times to ...
3
votes
1answer
62 views

Create index for multiple WHERE EXISTS subqueries

I have to find an efficient way to write a very specific query for an application that I'm developing. The idea is the following: Find all the genetic markers for which there exists at least one ...
3
votes
2answers
210 views

Adding 4th table to join jumps processing time from seconds to over 20 minutes

I am trying to join a total of 4 tables together. When I only join 3 of the tables together I get a result set of about 220,000 records in about 2 seconds, but as soon as I throw the 4th table in, the ...
1
vote
1answer
81 views

How to change aggregate function without duplicating SQL (by using SQL)

In MS SQL Server 2016 I have a scenario where data will be processed according to different aggregation functions in a large GROUP BY ROLLUP. I would like to have a stored procedure that has a ...
7
votes
3answers
51 views

Is it possible to have two copies of a table clustered in different arrangements seamlessly?

I have a table with around 100M rows. It only gets data inserted once/day but we need to do selects a lot. The selects are usually simple but need to return 100s of thousands of rows sometimes. It'...
0
votes
0answers
33 views

Calling stored procedure from ASP.NET MVC causes CREATE FUNCTION statements in Activity Monitor

Since updating to SQL Server 2016, some stored procedures have been behaving oddly. When run from SSMS they return results in one to two seconds. When run by an ASP.NET MVC web service they run ...
3
votes
1answer
79 views

Best practices, MySQL table with 150+ columns, many null

I have a table storing property data for thousands of properties, all coming from a feed. (updating at least once a day). I'm certainly not an expert with databases and would appreciate some guidance ...
0
votes
1answer
36 views

Updating records from the past with MySQL query

I've built an application that fetches reports from an external source. It downloads report data once a day. Each report covers the time from now to 30 days ago. E.g. let's say it's 1 May and report ...
15
votes
2answers
446 views

Why does Concatenation operator estimate fewer rows than its inputs?

In the following query plan snippet, it seems obvious that the row estimate for the Concatenation operator should be ~4.3 billion rows, or the sum of the row estimates for its two inputs. However, an ...
0
votes
1answer
117 views

Speed up query that have joined tables and function calls

I have a Bootstrap Table that use server side pagination to display results from a query like this: SELECT Item.a, Item.b, Item.c, Info1.Name, Info1.Name, Info2.Name, ...
2
votes
0answers
53 views

Procedure runs slower over time; fixed by cache clear or reboot

We are experiencing a strange issue where an application which was fixed by creating missing index requests, updating stale stats, and removing lookups and other scans, was running fine once fixed, ...
0
votes
1answer
46 views

What happens when the buffer pool size is insufficient in mysql

Let us assume I run a query for a table whose size is very huge. My buffer pool size is as low as possible. What happens now? whether I will get an error regarding the insufficient space in buffer ...
1
vote
1answer
85 views

Why is it faster to do four simple selects instead of one select with left joins?

I need to find a single value from a table A containing three foreign keys to two other tables B and C. For the sake of experiment, I tested two ways to query the value: Multiple queries: declare @...
0
votes
1answer
45 views

Does Oracle randomly switch execution plans to check if there is a better solution?

I had a talk with an external colleague about oracle "swinging in" its performance. In detail it was about, that oracle optimizes its execution plans for the same query by time. I don't talk about ...
1
vote
1answer
87 views

Troubleshooting extremely long running query (SQL Server 2012)

We have a purchased reporting application that executes a query that just recently is taking an extremely long time (>2 hours). A week ago, this same query completed in less than a minute. I've ...
3
votes
0answers
51 views

Do Large Hash Joins Contribute to Stolen Pages?

On a SQL Server 2014 SP1 Enterprise Instance, I'm performing an outer join between two partitioned tables on a numeric(16,0) + char(1) composite key. 100 GB is the max server memory setting on a 128 ...
1
vote
0answers
58 views

Simplify Month Over Month % Change, 4 Months Moving Average %

invoice created_at | amount | status | ------------+--------+--------- 2016-06-01 | 50 | 2 | 2016-05-30 | 150 | 2 | 2016-04-29 | 32 | 2 | 2016-03-28 | ...
2
votes
1answer
38 views

Optimal query to show active records by date

I'm trying to determine what the optimal query might be for associating a date with a record that would have been active for that day. Here is a setup to demonstrate what I'm trying to do (demo at ...
0
votes
0answers
55 views

Statistics shows CPU time = 0 ms, elapsed time = 0 on second time and query running blazing fast?

I tried to run this query on a database which is located on my network, but not on my own computer. set statistics time on SELECT id, status FROM MyTable EXEC MySproc @id='3000021' set statistics ...
1
vote
2answers
117 views

Consideration for a little bit heavy database

Environment information OS : Windows Server 2012 R2 ( 64bit ) RAM : 16.00GB CPU : Intel(R) Xeon(R) CPU E5-2609 @ 2.40GHz SQL : Windows SQL Server 2012 Standard Brief Database Data Information ...
0
votes
1answer
90 views

What is difference between JOIN and simple query

I have two tables in database one is Orders and another one is customers Orders Table Contains : OrderID , CustomerID and OrderDate Customers Table Contains: CustomerID , CustomerName , ContactName ...
6
votes
2answers
185 views

Running query against DMVs for Query Stats and Execution Plans joined to sys.databases

I originally posted this as a different question in Twitter #sqlhelp, but wanted to post it here differently. I'm trying to create a job that tracks worst performing statements for various statistics ...
0
votes
3answers
79 views

What is the performance impact of indexing a frequently updated column?

I just want to know if I'm doing this right. I've searched google for hours already and I can't find a straight answer. I have a table with potentially a very large amount of inserts and updates. Any ...
4
votes
2answers
683 views

Is it possible to rebuild a dropped index?

Is it possivle to drop and index, and rebuild it, instead of disable it and rebuild?
0
votes
0answers
67 views

how to find overlapping or duplicated indexes? when is it O.K. to keep them?

this is a script that does the following: create a database called "radha" for testing purposes, create the table ProductItemDetailsDenorm create the clustered primary key create ...
2
votes
0answers
101 views

Advice on how to improve this stored procedure

Edited: Added table column datatype I have 2 tables ReportItem id (int, primary key clustered index) report_item (nvarchar(100)) flow_name (nvarchar(50)) source (nvarchar(50)) Tech_Details id (...
2
votes
2answers
85 views

best way to avoid redundant aggregate functions and/or group by columns

Suppose I have two tables: Foo: id baz Bar: id foo_id boom So a Foo has many Bars. I frequently find myself in situations where I need to compute an aggregate across the Bars for a given set ...
0
votes
0answers
21 views

Example Database for tunning

I've been searching for so long and I've still have not found what I'm looking for ,is there any database or similar resource that people uses for tuning a database, or optimize queries?. I would be ...
1
vote
0answers
12 views

Efficiently get records with latest timestamp per group [duplicate]

I have a table which roughly looks like this uuid uuid, id id, data text, last_updated timestamp Each row has an associated unique uuid. However, the key of interest is the id (indexed). ...
0
votes
0answers
91 views

SQL query too slow to fetch single row of data

we have this SP, running extremely slow to fetch a single row of data from tables within 100K rows, which seems not that big. It takes onn avg 15-20 mins to complete. We have tried to remove all ...
1
vote
2answers
53 views

How to improve performance of a query with an IN subquery

Get the count of other users having the x tag with order_id in order_id of users having the y tag table: MyCustomTable (200K rows) order_id user_id type ('x' and 'y') my custom tags and the query:...
5
votes
1answer
152 views

Indexes: integer vs string performance if the number of nodes in the index is the same

I hope this is the right place to ask! I am developing an application in Ruby on Rails with the PostgreSQL (9.4) database. For my use case, columns in tables will be looked up very frequently, as the ...
1
vote
1answer
31 views

Subquery inside a select vs left join

Often I have to return the count of of some row in a query that fetch other non related rows. For example A table User a table Review and a Table picture User: id nickname Review: id to_user_id ...
6
votes
5answers
500 views

UNION ALL or other ways to return first row of result-set

I am writing a table valued function to geocode an address based on its Suburb, State and Postcode. I try to geocode the address using different methods, in order of decreasing accuracy: Exact match ...
2
votes
0answers
34 views

Materialized Views and Indexes

Is there any way to force PostgreSQL to use an index that I created on a materialized view table? I tried every combination possible of moving the column attributes around to make Postgres to use my ...
4
votes
1answer
21 views

Sort table rows and save the row numbers using UPDATE

I have Postgres 9.5 with a table movimientos that has the following data: | id | concepto | movimiento | numero | orden | | 1 | AJUSTE 1 | 2542 | 0 | 2 | | 2 | APERTURA | 12541 |...
2
votes
2answers
49 views

Improve query “JOIN … WHERE NOT EXISTS (SELECT 1 FROM … WHERE … )”

I'm trying to optimize a query because the plan generates a full table scan for a subquery. Data The (simplified) table structure: CREATE TABLE RECORD ( ID INTEGER PRIMARY KEY AUTO_INCREMENT ); ...
2
votes
3answers
113 views

Poor performance of JOIN, WHERE, ORDER BY combination (MySQL)

Goal: select 10 most recent rows from posts which are related to a specific user. There are two tables: posts (~5,000,000 rows) and relations (~8,000 rows). posts columns: --------------------------...
1
vote
2answers
39 views

Slow query / Indexes creation (PostgreSQL 9.2)

I have the following Query: explain analyze SELECT split_part(full_path, '/', 4)::INT AS account_id, split_part(full_path, '/', 6)::INT AS note_id, split_part(full_path, '/', 9)::TEXT ...
1
vote
1answer
27 views

index creation - Slow Query - PostgreSQL 9.2

I've got the following query: SELECT * FROM ( SELECT split_part(full_path, '/', 4)::INT AS account_id, split_part(full_path, '/', 6)::INT AS note_id, split_part(full_path, '/', 9)::TEXT ...
0
votes
1answer
54 views

MySQL Query fix and speed up

I'm newish to MySQL and a lot of my query is pieced together from this site and trial and error, so any help is appreciated. If I left out anything, or more detail is needed, I will be happy to give ...
4
votes
1answer
164 views

How can I speed up a stored procedure?

Here is an interview question I just had. I would like to know what a good answer to this would have been and what the different options would be. We have a stored procedure that is taking 26 ...
4
votes
1answer
103 views

How can I optimize a query with multiple derived tables containing `IN` and `GROUP BY`?

I'm collecting nmap data every five minutes and storing it in a database. Information about each scan (e.g. start and end time) is stored in the scans table: CREATE TABLE `scans` ( `scan_id` int(10)...
3
votes
2answers
79 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 ...
6
votes
3answers
120 views

Query wont compile/run

I have a query that won't run on the production server but it runs on the test server. It seems like the query plan won't compile or its compiling a very bad query plan. I have updated all statistics ...
1
vote
1answer
44 views

Can the subquery be simplified/optimized?

Here's a simplified version of a query I run. I've removed a bunch of key/value pairs for simplicity. The constraint is that I can't change anything outside of the ARRAY function; but the ARRAY ...
1
vote
1answer
19 views

Joining on a M-N lookup table vs keyword searching a single column

I am in the process of writing an image gallery webapp similar to that of Danbooru, and in the process, decided to take a look at danbooru's database schema for an idea about how things are structured....
0
votes
0answers
39 views

best practice to remove leading zeros when writing data to a destination

I have a query like in my other question DBA Question with Source Code of Select statement And i want to remove the leading zeros of the customer Number (KUNDE) with the answer of this question (...
0
votes
1answer
79 views

Need help improving query performance

I have this simplified version of my database: http://sqlfiddle.com/#!9/4b903/2/0 I have a million rows in history and my problem is the query is so slow. It would take more or less 2 minutes. I'...