I am using the SQL module of Qt 5.3.1 (Win 7, VS2013) to insert data into a MySQL 5.6 database. After I noticed some performance issues I execute three test code snippets and measured their runtime...

I'm looking to create denormalized access to data essentially for reporting purposes (and thus to avoid joins and gain performance). I have two solutions in mind, but I'm looking for (a) other pote...

My Google cloud sql table have 1126571 rows currently and adding minimum 30 thousand every day.When execute the query : select count(distinct sno) as tot from visits sql prompt it will generate ...

I am using MySQL Connector/Net 6.5.4 with LINQ to entities, and I frequently get terrible query performance because the entity framework generates queries that use derived tables. Here is a simpli...

NewRelic gives nice database analyses, however it seems to track only the web app's transactions. I have independently managed servers which query and load my Heroku postgresql database. Is there ...

Does anyone know if there is a difference in performance for left join vs inner join in Hive, with Map Join enabled via hive.auto.convert.join=True? The reason I ask, per https://cwiki.apache.org...

I want to select to retrieve person and also further make some inserts, deletes and updates. If I want retrieve person who lives in Brazil what will be the best approach? Make 2 foreign key city ...

I'm reading this article on Wikipedia: http://en.wikipedia.org/wiki/Shard_(database_architecture) trying to find the major difference between these 2 techniques. Here is what I found: Horizontal...

I'm using the RDS database from amazon with a some very big tables, and yesterday I started to face 100% CPU utilisation on the server and a bunch of slow query logs that were not happening before....

I have quite a simple query that is very slow. Entity Framework Profiler says it takes about 100 ms. dbContext.Users.Single(u => u.Id == userId); After trying around a bit I found a query tha...

In SQL Server, stored procedures execution plans are cached but view execution plan are never cached. Is that true? If yes, why does SQL Server not cache view execution plans? If a optimizer is ta...

I have a very simple query that returns a couple thousand rows with only two columns: SELECT "id", "value" FROM "table" LIMIT 10000; After issuing sql.Query(), I traverse the result set with the...

I'm running a cron task which makes lots of queries to a MySQL server. The big issue is that the server runs extremely slowly sometimes. I've got a relatively big query with 4 tables left joined b...

I had a query like this, that should be executed after each MySQL actions. This query is now slowing down page loading because the data increased, I did everything like proper indexing, but the que...

The queries are performed on a large table with 11 million rows. I have already performed an ANALYZE on the table prior to the query executions. Query 1: SELECT * FROM accounts t1 LEFT OUTER JOIN...

I have always heard people saying bad about using cursors and this is especially in Microsoft SQL Server as they are very slow. Is this the case with Cursors on MySQL as well? Does cursors in...

I'm facing a problem with MS SQL Server 2008 which is: When I execute a query using a hard-coded string as a parameter, my query run fast but when I use a string parameter instead, the query takes...

So my understanding of slow query log is that it logs info about all those queries that took >= time (in secs) that we have set in my.conf file. Now lets take 3 cases of 3 different SELECT queries...

I'm attempting to write a search functionality for a website, and I've decided upon an approach of using MySQL temporary tables to handle the data input, via the query below: CREATE TEMPORARY TABL...

Given this SQL query in MySQL: SELECT * FROM tableA WHERE tableA.id IN (SELECT id FROM tableB); Does MySQL execute the subquery SELECT id FROM tableB multiple times for each row in tableA? Is t...

I'm implementing an app that keeps track of how many times a post is viewed. But I'd like to keep a 'smart' way of keeping track. This means, I don't want to increase the view counter just because ...

I need to store several billion small data structures (around 200 bytes each). So far, storing each element as a separate document is working well, with Mongo providing around 10,000 results per se...

What is the fastest way to load 10,000 rows from a SQLite database into memory? Each row has 1 text and 4 integers. Currently, I'm doing this: while(!cursor.isAfterLast()) { cursor.copyStringToBu...

When I create DECIMAL column with default precision setting, in H2 web console this column is defined as DECIMAL(65535, 32767), command "show columns from ..." gives me DECIMAL(65535). Decimal dat...

So I have a table with a large dataset and this table has a three columns that I would like to drop. The question is: how will Postgres deal with it? Will it walk through every entry or will it ju...