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

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884 views

Query that only uses index takes long time to execute [closed]

I have a table with ~69,000 rows. I have this very simple query: -- SET STATISTICS TIME ON SELECT ID, FirstName, LastName FROM Customers -- SQL Server Execution Times: CPU time = 31 ms, elapsed time ...
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2answers
415 views

Query gets slow when bind peeking is turned on

There is an old database that was upgraded from Oracle 10 to 11G R1. In Oracle 10 we had disabled bind peeking. Since Oracle 11 has adaptive cursor sharing, we want to turn bind peeking back on. When ...
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1answer
138 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 ...
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1answer
1k 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 ...
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2answers
94 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 ...
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1answer
87 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)) = ...
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1answer
658 views

Filtering records not present with specific conditions in another table

I have a table (let's call it extra_info) in MySQL that has various extra infomation/labels on user accounts: account_id / data_key 11 / 'test' 11 / 'blah' 12 / 'coupon a' 12 / 'coupon b' 15 / ...
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242 views

How can I increase performance for select in select statement

The item table is like this id category_id name registered I have to show total number of items from the beginning. Suppose between 2013-05-01 to 20-05--05, I have to count all the items ...
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1answer
129 views

Looking for performance improvements for this query

This query is taking a long time to execute. We are expecting results in 0 sec, if possible. Please help me to do any other following: Rewrite the query Suggest any indexes Any other optimization ...
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2answers
396 views

Large time difference between two almost identical simple queries…why?

I'm trying to understand why is there so much difference in execution time and CPU usage between two simple queries that only differ in a computation. The queries are the following: SELECT ...
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1answer
296 views

Create a VIEW that spans 3 tables

Sorry if the title is not clear - feel free to improve. Here are 3 tables (not all data is relevant to the question): CREATE TABLE `content` ( `id` int(10) unsigned NOT NULL AUTO_INCREMENT, ...
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1answer
346 views

Design database to query a date range for scheduling

I am designing a db that should include a table with fields for datetime scheduling, so as I know what kind of queries will be made​​ periodically I would like to design the table for them to be as ...
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2answers
208 views

How can I optimize this query and support multiple SKUs?

My current query only can select one SKU at a time. I can leave salesite_id constant. If there is a way to also have varying salesite_ids that would be good too, but not necessary. Also any ...
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1answer
199 views

Is possible to optimize this query or it's already optimized?

I've three tables: default_users, default_profiles, default_friend. This are the SQL for each one: -- -- Table structure for table `default_users` -- CREATE TABLE IF NOT EXISTS `default_users` ( ...
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1answer
1k views

Slow performance of MySQL Join Query

I have inherited a site (running Coldfusion8 and MySQL 5.0.88) with a product search using multiple criteria. I'm struggling with optimizing the search, especially a pricelist check, which makes the ...
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1answer
194 views

MySQL query took 98 seconds to run but EXPLAIN looks okay

I have a query that took 98 seconds to execute this morning, but I can't recreate the problem now, and the EXPLAIN output isn't giving me any clues. Am I missing something? Here's the SQL: SELECT ...
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1answer
161 views

Creating Indexes to optimize query

I have this query and I want to increase its performance by adding appropriate Indexes. DELETE FROM MYTAB1 WHERE MYID1 IN ( SELECT MYID2 FROM MYTAB2 ); I am not familiar with the ...
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1answer
16 views

represent multiple entities to one entity relationship

If suppose, I have following tables: Here, person can own either home or car. person can't own both at a time. If person owns home, then owns field will be equal to 1, if it owns car, owns field ...
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1answer
58 views

Complex query performance in MySQL InnoDB versus MyISAM

I am running on MariaDB 10.0.15 on a 4GB RAM cloud server with Local SSD disk for database. My model: users <n---n> right_holders <n---n> tracks ---n> raw_detections I have this ...
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1answer
62 views

How to speed up mysql query against a 204 million record table

For some reason my server has been finicky lately and for the life of me I can't figure out why. I monitor the memory usage by running shell# watch -n 5 free -m without running any activities ...
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1answer
44 views

MySQL - How can I improve this query? EXPLAIN attached

I have a query that I feel should go much faster then it does. Right now it'll execute around 1,5xx secs each time. I don't have any advanced knowledge of looking at the EXPLAIN and draw conclusions. ...
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1answer
109 views

Why does MariaDB 10.1.2 blow away MySQL 5.6.22 in sysbench?

Problem Maria DB is doing roughly twice the number of transactions that mysql is using standard oltp benchmark. The VM and db's are both fresh installs from vendor apt repos with default configs. ...
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1answer
35 views

How bigger page size effect at performance?

I know in case of Cluster index bigger page size improve peformance for range and multipoint query. Does bigger page size can effect to degrade performance when we have non cluster index .Because ...
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1answer
68 views

How database buffer pool work?

For example we have 2 scenarios: Scenario 1:- We have very small buffer pool size of 100MB. My query data is 500MB. Does the system keep 500MB query data in RAM such that a new ...
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1answer
202 views

Columns count in SELECT query and SQL Server buffer cache

Let's assume that I have a table with 30-50 millions records. It has ~40 columns. Currently when I request data it always requests all columns because of legacy ORM that we use. I know that if we ...
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1answer
40 views

Mysql query performance

We have a database table and we found a weird query from old code. We can't really explain it, so we decided to analyze why it could have been done that way. The weird thing is that the results are ...
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1answer
109 views

Slow running aggregate of aggregate query

I am looking for the total balance for all accounts that had a negative balance as of a specific point in time. I've already got the code below, and it works, but works horribly. The transactions ...
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2answers
90 views

Find the closest bar, when searching for a drink

Problem: Find the closest bar that serves the drink(s) I'm looking for. Here you can find the generated MySQL code http://pastebin.com/5Uc2ewUW The API Request that interacts with this problem ...
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1answer
149 views

How to increase sql server performance? denormalization (making cascade delete off) vs making duplicate data

I have a database with following related table ( sql server enterptise edtion 2014) each state have many citites which each city has may municpalArea and so on State => Cities = > ...
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1answer
71 views

The materialized view is already optimal and cannot be tuned any further

I have tried DBMS_ADVISOR.TUNE_MVIEW to verify some materialized views created locally. One of the result returns an error: Error report: ORA-13600: error encountered in Advisor QSM-03116: The ...
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2answers
132 views

Best way to store few rows of data every minute without creating 1440 columns a day?

I will be calling a server that returns some JSON data every minute. The values are along the lines of Value, Currency, DateTime, and maybe 1 or 2 more values. What is the best way to keep save these ...
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1answer
73 views

If a query contains two identical subqueries, will they both run?

Say I have a SELECT query that contains two identical subqueries, like the below: SELECT (SELECT SUM(Price) FROM Product p WHERE p.GroupID = g.GroupID) AS 'TotalCost', (SELECT SUM(Price) ...
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1answer
64 views

How can I time SQL-queries using psql from command line?

I am sorry, I cannot comment, so I am posting a new question. There is already a question "How can I time SQL-queries using psql?" but I am missing answer how to do that from command line. How to run ...
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1answer
228 views

PostgreSQL - If I run multiple queries concurrently, under what circumstances would I see a speedup? Under what circumstances would I see a slowdown?

I approach you all humbly as one who is NOT a DBA, and I'm sure that my question is fraught with conceptual shortcomings and "it depends on" land mines. I'm also pretty sure that all of you who ...
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3answers
169 views

Why is my select statement so slow?

SELECT name FROM sys.databases WHERE name not in ('master','model','msdb','tempdb','ReportServer','ReportServerTempDB','1303VISBOC') AND CASE WHEN state_desc = 'ONLINE' THEN ...
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1answer
96 views

Last row from a query without Order by

I have something like SELECT var1,var2 FROM table where var3=X AND var4=Y order by var5 desc limit 1; Running this query takes roughly 5 seconds on my database which is far to slow. I was ...
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1answer
35 views

How to optimized mysql query having large dataset

I have two tables in MySql with the following schema, CREATE TABLE `open_log` ( `delivery_id` varchar(30) DEFAULT NULL, `email_id` varchar(50) DEFAULT NULL, `email_activity` varchar(30) DEFAULT ...
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1answer
84 views

Help optimizing very slow mySQL query

I have a query which takes about 6 secs to execute. SELECT * FROM (SELECT ord.ID, op.name AS prodName, op.code, ord.date, ord.email, op.total, stat.ID AS statusID, stat.value AS status, ...
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2answers
508 views

Increased query_cache_size, Queries slowed drastically on increased traffic

I increased our servers query_cache_size to 2gb, hoping for performance benefits. After sometime the query performance would drastically decrease. Once I dug in deeper, I found the queries in State ...
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1answer
54 views

How to optimise very simple query with subquery that only needs to execute once

SELECT products_id, products_model, products_iban_no, products_allocation_number FROM products WHERE products_model IN (SELECT products_model FROM products GROUP BY products_model HAVING ...
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1answer
426 views

Couldn't find the long running SQL under v$session_longops

I have following SQL running from a long time. I couldn't see the status When I tried to look the time remaining for the query to complete. Can someone explain me why I couldn't find the SQL status ...
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1answer
231 views

Query with INNER JOIN takes long time than expected?

I have the following query, which takes longer than expected. Anybody help me find a faster alternative? SET SESSION MAX_JOIN_SIZE=18446744073709551615; SELECT claims.claim_id, ...
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1answer
170 views

too many entries for one single session and serila# in V$Session_longops

I have a concern with the entries in v$session_longops. I used a query to identify query running from past 25 minutes for sid=62 which is given below: SELECT s.sid, s.serial#, ...
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2answers
223 views

Instead of static list, using a table select result for IN key

I use a static list for some queries WHERE clause like WHERE STypeID IN ('12', '13', '14', '265') This list will be changed in the future; new values will be added. When list changed, I don't want ...
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1answer
46 views

Oracle Autodop disabled at the table level

I have a question related to Oracle auto DOP and parallel DML concepts. I have a scenario, if I set the Auto DOP set to 1 on the table and if I run parallel DML statements on that table through ...
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1answer
81 views

MySQL: What points should we consider when create composite index

There are multiple views behind the logic of creating composite index in a table. Creating composite index is obvious when we have composite primary key. Beside this, we create composite index on the ...
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2answers
80 views

How should I structure my time based index?

So I have this table in SQL Server 2008. Let's just say it's called TimeSheets. Now, that table has two columns I am concerned with. TimeSheetDate and UserCustomerKey. TimeSheetDate is a ...
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1answer
339 views

What is the Difference between IN and Not IN performance wise?

I am new to database.I am having doubt that what is the difference between IN and NOT IN performance wise. When I am using IN, takes less time for the same query(Logically same query) when I use NOT ...
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2answers
569 views

MYSQL - Why does this SELECT get slower the further down the table?

My table: CREATE TABLE `wp_users` ( `ID` bigint(20) unsigned NOT NULL AUTO_INCREMENT, `user_login` varchar(60) NOT NULL DEFAULT '', `user_pass` varchar(64) NOT NULL DEFAULT '', ...
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1answer
71 views

How can I efficiently search for all records from a given month, or a given year?

We have a couple queries that involve datetime fields. In particular, we are checking for things like SELECT field1, field2, ..., field20 FROM table WHERE MONTH(startDate) == 1 SELECT field1, field2, ...