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

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2
votes
1answer
1k views

How to optimize a very slow query with joins and group by?

I have this GTFS database : All the ***_id columns are indexed, and there are foreign keys between tables (such as a FK on trips.route_id to routes.route_id). So basically the link between a stop ...
2
votes
1answer
503 views

Improve select query performance

The following select query from my application is taking more than 200ms. The table has around 2 million rows. Is there any ways to improve the performance of this query ? select count(id) from ...
2
votes
1answer
3k views

How to use LOW_PRIORITY for heavy queries?

I have scheduled heavy UPDATE queries at administrator level, and since they are heavy UPDATEs with multiple JOINs, consume a huge amount of resources. I do not want them to stop end users from ...
2
votes
1answer
1k 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
4answers
16k 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, ...
2
votes
1answer
66 views

What is the algorithmic complexity of a PosgtreSQL greater than or lesser than index query (compared to equality)?

Assuming there is an index idx_int on an int_col column, what is the algorithmic complexity of a query like this? SELECT id FROM table WHERE table.int_col > 1; I'm specifically interested in ...
2
votes
3answers
800 views

Why is SQL running the same query longer from another connection? [closed]

Here is the issue overview: Why does my stored procedure run faster when executed localy vs remotely? Dont jump to any conclusion just yet, let me explain what I mean... Here is the setup: A Windows ...
2
votes
1answer
470 views

Slow query performance

My database contains 20,000 rows and the following query is slow. Please help me to speed this up: SELECT r.report_id, r.user_id, u.user_name, u.user_mail, ...
2
votes
1answer
2k views

Oracle 10g using collection with sql

I have a stored procedure that takes collection of objects. (TABLE OF MyCustomType). Inside the procedure I'm trying to join this parameter with real tables. For example, something like create or ...
2
votes
1answer
1k views

oracle merge operation hangs (or loops); query tuner claims it's a cartesian product operation

I have a Merge query (open to better suggestions) that seems to cause the server to hang. (I'm not sure what it's doing, but it pegs the CPU and never completes) When I run it through the query ...
2
votes
1answer
2k views

Slow complex query with group/order

I have a problem with a very important query in my application. It is very slow when adding group and order to it. So the full query is: SELECT m.id, m.title, m.title_text, ...
2
votes
1answer
256 views

What would be a optimal index for this query in mysql

I'm trying to optimize this query. SELECT * FROM sales_reps WHERE account_id = 1 AND (state = 'enabled') AND (clients >= 5 OR revenue >= 10000) ORDER BY name, platform, client_group, ...
2
votes
1answer
136 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 ...
2
votes
1answer
109 views

Get the id_user_app if not exists in id_user_rq

I'm building a application and have this table for users relationships. I need to build some queries like for example: Who invited me as a friend? Who I invited to be my friend? Who I accept as ...
2
votes
1answer
1k views

How to calculate query that access system view cost in Oracle?

For a query that returns if there are any active transactions within current session , SELECT COUNT(*) FROM v$transaction t INNER JOIN v$session s ON (t.ses_addr = s.saddr ) INNER ...
2
votes
1answer
290 views

datetime index skipped for same query different params

I am running two queries with same query but different parameter and one of them is extemely slow while the other is fast. Both the results are alomost the same. (500 and 575) Any idea why it skips ...
2
votes
1answer
390 views

Rewriting a query

I have a database with the following structure (star schema): facttable: pros integer mena integer me integer vahet double precision slutttp timestamp without time zone Structure of each ...
2
votes
0answers
99 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
0answers
26 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 ...
2
votes
0answers
41 views

Order by index unexpectedly slowing query down

I have two tables: houses has ~415,000 records, and account_houses has ~525,000 records. I've changed the table names for security reasons, but basically I am using this query: SELECT "houses".* FROM ...
2
votes
0answers
46 views

where to add a column with low cardinality, decimal type into an index?

I got a question regarding the best way to put a bad column for an index in an index, so that I can satisfy my query below, and similar others that follow the same pattern. on the query below, all ...
2
votes
1answer
84 views

SQL Query for Internal Messaging System

I'm creating an internal messaging system (No SMTP/POP3) and I'm looking for a way to query a user's list of messages. Here's my schema: Messages _MessageID (PK) _MessageParentID (if a reply this ...
2
votes
1answer
37 views

Excluding rows by lots of ids

I need to exclude some rows that the user has already seen. Currently I am doing this by simply comparing the ids that the user has seen to the row's ids by running this query (there are also other ...
2
votes
0answers
40 views

Composite index works for larger set of data, but not smaller

This is a follow on question to optimise my.ini for key query Data model: DROP TABLE IF EXISTS `contract`; CREATE TABLE IF NOT EXISTS `contract` ( `id` int(11) NOT NULL AUTO_INCREMENT, ...
2
votes
2answers
67 views

Finding differences between two tables takes too long

I'm trying to find the diff of two tables using a left join. My query is as follows: CREATE TABLE my_diff (INDEX my_index (name, type)) SELECT AA.name, AA.type FROM AA LEFT JOIN BB USING (name, ...
2
votes
0answers
122 views

Two queries usually run fast but get slow when joined

There are those 2 tables CREATE TABLE IF NOT EXISTS `media` ( `mid` int(11) NOT NULL AUTO_INCREMENT, `user` int(11) NOT NULL, `order_type` int(11) NOT NULL, `media_id` varchar(50) COLLATE ...
2
votes
0answers
90 views

Improving performance of a weighted search query in SQLite3

For an intra-site search I have this table in an SQLite3 database, that relates ids to search terms with a certain weight: CREATE TABLE search_index ( id INTEGER(7) REFERENCES other_table, ...
2
votes
1answer
112 views

Slow PostgreSQL query

I'm building a search interface for a web site that currently searches through approximately 2 million pieces of real estate with approximately 60 million attributes (address, city, state, ZIP, beds, ...
2
votes
0answers
315 views

Why is this MySQL query “using where” instead of “using index”?

Could you help me with this query, please? SELECT p.patid, MAX(c1.eventdate) as eventdate from patient as p left join op_adv_effects._clinical as c1 on p.patid = c1.patid left join ...
2
votes
0answers
69 views

Performance differs on same query against two (almost) identical tables?

I'm running these two queries in SQL Server 2012: SELECT tpua.Field1, CAST(round(twg.Field2 * 2, 0) / 2 As Decimal(8,1)) As Field2, CAST((round((twg.Field3/10.0) * 2, 0) / 2) * 10 As int) As ...
2
votes
0answers
31 views

Query optimization - contact should be extracted at most once for a particular customer

I have created a database for a telemarketing company Scenario is, the telemarketing company is selling contacts to the customers. Customers log on to the website and search for the contacts for ...
2
votes
1answer
574 views

SQL Server 2012 stored procedure runs very slow sometimes

I have a stored procedure with a single large query which takes an ID as a parameter and returns some counts. It has quite a few inner joins and left outer joins but they are all on indexes. The ...
2
votes
1answer
182 views

Updating large table worked before, now taking hours

BACKGROUND: I am using a non-production SQL Server to manipulate a large data set and run a few basic calculations. The original data file I have, which is about 30M rows, is missing records (not ...
2
votes
0answers
196 views

Oracle instead of trigger update performance issue

I have a large table containing over 15million records with 4 columns that form a compound key. Because we use a development environment that doesn't support compound keys I was required to create a ...
2
votes
1answer
145 views

Retrieving latest record using DISTINCT ON is slow [duplicate]

Using Postgres 9.4. I have a table cartests with 5.5M rows. Each row is a car test: \d log.cartests; Table "log.cartests" Column | Type | Modifiers ...
2
votes
0answers
94 views

select on table slows done during update on same table [closed]

I have a weird problem with mysql. During a transaction which runs from 10-30s around 270 statements are performed, some of which are updating and inserting a few rows on a table. If a select is ...
2
votes
1answer
75 views

PLSQL using cursors or functions to query repeated data

Is it better to declare a commonly used lookup query as a package function or as a function (either returning rows or values or returning a sysref cursor)? Whats the difference? What are the best ...
2
votes
1answer
155 views

MySQL: Why queries with subqueries are much faster than single query?

I made few queries on my db lately First query: SELECT `table`.* FROM (`table`) WHERE table.id in(27172172,[...bunch of ids...],27171770) ORDER BY field (`table`.`id`, ...
2
votes
0answers
68 views

Optimization suggestions for db2 materialized view

I have a view for db2 9.7 which has consolidated o/p from few tables. The view is built and it is working fine I want optimization suggestions on the view SQL CREATE VIEW XYZZ AS SELECT ...
2
votes
0answers
148 views

Almost identical queries but large time difference in execution

Exhibit A SELECT SUM(value) FROM Credits RIGHT JOIN calendar ON datefield = DATE(FROM_UNIXTIME(created_at)) WHERE confirm = 1 && reason = 1 && country = 'it' && created_at ...
2
votes
0answers
54 views

Emulating WITH clause in MySQL/query perfomance review

I have never really worked with MySQL queries till this last week. I was tasked with making a simple tool for my department that tracks contacts. Here are the 2 tables and the type of data they ...
2
votes
1answer
218 views

High I/O for part of query

I have a large query that I'm trying to tune. I write lots of queries but haven't done a lot of tuning. I've included a screenshot from SQL Sentry Plan Explorer Free (SSPEF): In the above part of ...
2
votes
2answers
2k views

Improve MySQL Query Performance - Too many records

I am using MySQL RDMS for a contact management system. Now a days my database grew in size and contains more than 1 million records. Checking duplicate phone numbers became a big issue during ...
2
votes
0answers
630 views

mariadb out of memory crash

I have recently migrated from mysql (5.5.36 MySQL Community Server (GPL)) to MariaDB (10.0.10-MariaDB-1~wheezy), along with switching my cloud hosting provider. Both machines have 2GB RAM and 1GB ...
2
votes
1answer
659 views

Optimize table and query, aggregate by date or date-hour

I have a table storing sensor data (100M rows currently) from stations from different sites. In my case, sites may have many stations. Create table statement is as follows: CREATE TABLE sensor_data ( ...
2
votes
0answers
235 views

Does Oracle ADO.NET varchar parameter size influence query plan reuse?

I am considering to apply a fix which will generate constant parameter sizes for (n)varchar parameters. The application is based on NHibernate with the old OracleClientDriver (using Microsoft Oracle ...
2
votes
0answers
81 views

Single table row “sharding/versioning” to customize values

Introduction Hello everyone, I have done quite a bit of searching and I cannot find a solution for my specific issue. There are a few factors that complicate my situation, which I have outlined ...
2
votes
0answers
268 views

PostgreSQL 9.2 (PostGIS) performance problem

A month ago i got acquainted with PostgreSQL and only now i've noticed that some of my queries are pretty slow. Well, for example, i have table: CREATE TABLE sometable ( gid serial NOT NULL, geom ...
2
votes
3answers
6k 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
0answers
449 views

Read vs. Write speed

In the data import procedures I have, I get external raw data and import it into tables. I don't just overwrite the data, even if it is only from one source, but before I allow an update, I check if ...