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

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40 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
28 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
39 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
31 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
36 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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1answer
45 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
22 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
70 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
72 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
41 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
118 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
74 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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2answers
233 views

postgresql being slow on count distinct for dates

I have a very simple, but very big, table. Its schema is like this (yadda int, yadda1 int, yaddate date, ... other stuff). Now, yaddate has an index by itself and it is also in other indexes ...
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1answer
61 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
117 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
22 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
58 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
65 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
249 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
477 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
49 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, ...
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2answers
473 views

MySQL: why assign NULL as default value

When we define a table, multiple times we assign default value of a column as NULL. I have How NULL is different than empty value('') as well as 0? Is there any impact of NULL value in query ...
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1answer
83 views

Sequences Vs Count for auto-increment

Can some one please tell me the exact difference between the following statements , INSERT INTO table1 VALUES ((select count(column-name) from table-name2)+1); here i am using the count function to ...
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1answer
71 views

Query a name in large database, optimizations? [closed]

if you would like to query a name in a very large database, are there some ways to optimize this query? If 1 million names are in the database, and the name has to stay as it was registered (and not ...
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1answer
83 views

Index being ignored by Oracle

I have a table for sensor data, simplified it looks like this: DEVICE_ID NUMBER SENSOR_ID NUMBER DATA_TIME NUMBER DATA_VALUE1 NUMBER The table constains billions of rows and is partitioned by week ...
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1answer
1k views

Different execution plan for the same query if I change a value in the predicate

I am getting two different execution plans for the same query only by changing the value in the predicate, the first one uses nested loops and the other one hash join which takes a lot longer. ...
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1answer
301 views

Simple PostgreSQL lookup table is inexplicably slow

I'm trying PostgreSQL 8.4.14 for storing triples, pieces of data of the form (String, String, String). For speed, I'm not repeatedly storing strings but rather using two tables: main table triples ...
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1answer
99 views

Using an enum index to limit records

A common issue, just not sure on the keywords. I have a table of assessments (14k+ records). Each assessment can be in many different states ('draft', 'proofing', 'amends', etc... and 'done'). Most ...
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1answer
152 views

Efficient way to write query for multiple table which depends on column value of a table in mysql?

In the given schema, there is a table A having column A1,A2,A3,A4 There are three more tables i.e. B,C,D If the value in A4 is b, i have to lookup table B. If the value in A4 is c, i have to lookup ...
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1answer
197 views

T-SQL Gurus, I need help optimising these queries for performance

I would like to have suggestions on improving the performance of some queries. These will be run on SQL Server 2008 R2 against a single table called dbo.bids In a production environment the table ...
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1answer
46 views

Query Optimization for added value

I have a query that's behaving a bit oddly. In my database I have a table called "records". It tells me a bunch of information about what applications a user ran on my company's machines. I'm ...
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1answer
52 views

strange “using where” in simple query

I have a table with this structure: mysql> describe user_groups; +----------+----------------------+------+-----+---------+----------------+ | Field | Type | Null | Key | ...
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1answer
28 views

Condense Query Results with Wildcard

I have the following query: select programVersion, count(programVersion) from records R inner join Programs P on P.programID=R.usageProgramID where programName="word" ...
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2answers
806 views

How to use and optimize subquery on 100 million rows

What I'm trying to do is running a job on more than 100 million domains which haven't processed before. I have two tables, "domain" and "domain_setting", on every batch (10.000 domains per batch) I'm ...
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1answer
49 views

Optimizing Query

Can anyone help me tuning this query..... explain extended SELECT DISTINCT a.msisdn FROM `std_msc_opr_wise` a LEFT OUTER JOIN (SELECT msisdn FROM as_treat_pre_usage_30days GROUP BY ...
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1answer
124 views

What is the correct model for related tables with millions of rows?

I need to create a question and answer tables that will have millions (maybe billions) of rows. The current model is: Question Table id_question (PK, auto increment) id_user question_content ...
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1answer
222 views

MySQL stored routine performance while using PREPARE

Instead of maintaining stored routines for each database in my current environment I have decided to create separate database just for stored routines storage. Mainly I am using them for reporting. ...
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1answer
25 views

Simple query not using indexes

My query is not using indexes. It is a simple query. Can someone explain why that's the case? The query: select TIME_FORMAT(start_time,'%H:%i') start_time, TIME_FORMAT(end_time,'%H:%i') ...
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1answer
96 views

speeding up a query on MySql [closed]

I have a table with more than 10 million rows and 10 fields(columns). There is an index on field_1 and I am running the following query. create table t2 select field_1, sum(ifnull(field_2,0)) ...
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1answer
81 views

Speed efficient query for membership first joined, latest category from membership table (min, max)

I have the following table representing membership information: CREATE TABLE IF NOT EXISTS `membership` ( `id` int(11) NOT NULL AUTO_INCREMENT, `organisation_id` int(11) NOT NULL, ...
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1answer
368 views

slow queries - set weight to token type in tsquery - postgresql

Postgresql version 9.2.3! I'm working on a database for mapping of chemical names. My main table contains aprox 91 million records and it's indexed by gin. I want to query it with multiple names (I'm ...
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1answer
64 views

Faster joining on 'most recent' related rows

I have a bug tracking application. The bug table stores very little, because every state change to a bug happens by adding a comment. For example, the current state of a bug is determined by the state ...
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1answer
112 views

Query taking long time

My query is taking around 540 seconds to get result. Please help me to rewrite it. Query: SELECT pd.domain, fd.passkeyid FROM portfolio.domains AS pd, fabulousdomains.domains AS fd WHERE ...
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1answer
126 views

Reviewing all new MySql queries on staging environment

The problem I am trying to solve: It's well known that not all developers know what is EXPLAIN in MySql, and not every knows how to use it. Large part of them consider MySql as a black box, no matter ...
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1answer
273 views

MySQL Partition based on month-year

Is there a way that I can create a month-year partition on the below table? Without having to define all the permuations of month/year combos ? CREATE TABLE visitor_visits ( id int(10) UNSIGNED ...
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1answer
2k views

Is there an easy way to debug and find out why a query runs slow?

I'm running onto a weird issue. We've got two db servers, one is development and the other one is production. Both have same specs. VMs (Hyper-V) Windows Server 2008 R2 64 Bit SQL Server 2008 R2 64 ...
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2answers
221 views

Attempting to avoid SORT in query planner

I have a query that is used VERY frequently in my application. Without modifying the query itself, I'm trying to optimize it by toying with different indexing schemes. Here's the query (basically): ...
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1answer
134 views

Help me to better design my query so I can gain more performance

I need to find so called first entry in database for items regarding their partners. I wrote query and it is giving me correct results but it sucks with performances. I suspect that I have missed ...
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1answer
346 views

Returning Multiple Result-Sets or Single XML Blods

I've been writing some new Stored Procedures, and find myself returning between 6-8 result-sets in a few cases. I've always worked under the assumption that there were certain inefficiencies with ...
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0answers
6 views

Design and queries for analysis of event-sequences

I will have to store sequences of events with certain properties in a database (MariaDB preferably) and I have some issues regarding the design and queries. The crucial part is the analysis of the ...