MySQL : Open-Source, Relational Database Management System

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Does having many databases affect MySQL performance?

I have huge unused databases in MySQL. Do they affect my MySQL engine performance even if they are unused? Do they consume memory on their own? Thanks
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Can I estimate the row count of a large mysql table using the disk space?

Sysadmin here (not a developer by trade), so go easy please ;) I have a mysql table, on a linux server that uses innodb_file_per_table. When I try to do select count(foo) from table; It doesn't ...
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How to store temp tables in memory during table “optimize”?

When optimizing tables, SHOW PROCESSLIST lists it as "copying to tmp table". I'm trying to ensure the copy takes place in memory to speed up the process. I've tried adjusting the tmp_table_size to ...
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MySQL ran out of space, now won't start

So the partition MySQL was mounted on ran out of space. As a quick fix, I decided to move mysql's data directory to /home/minecraft/mysql/. I then changed the datadir in the config to the correcy ...
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Relational modeled design to store versioned files

The scenario I have images in a database table and some of these need to be altered then re-saved(not overwriting the original) whilst providing a reference back to the original. I also save the ...
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No privileges on the admin

I am using MySQL on AWS, and I came to horrific realization that privileges were flushed shut N across the board today. I was able to view this from an other user has very few privileges, but one of ...
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Will redirecting queries to dev/null warm up indexes?

I'm trying to warm up the buffer pool. Will running a query and re-directing the output to /dev/null suffice? e.g. mysql -u username -p -e "select id from tbl where 1=1" > /tmp/results.txt Thanks
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Issues with Inserting due to FK constraints

I have two tables: Employee, and Department. They are setup like so, : CREATE TABLE IF NOT EXISTS `mydb`.`Department` ( `Dname` VARCHAR(25) NULL, `Dno` INT NULL, `Total_sal` INT NULL, ...
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21 views

SQl comand works in Workbench but not from Java Program

I am working on a program that manages a database of client information. I am currently stuck on a problem where the SQL statement created by my java program but get the error SQLException: You ...
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26 views

“Display width out of range for column” error when importing mysql 5.1 dump into 5.5

I am migrating to a new server, and trying to move my database from a 5.1 to 5.5 server. I created a dump with mysqldump -u root -p --add-drop-database --triggers dbname > dbname.sql When I ...
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46 views

Avoid transaction rollback when Deadlock is encountered (mysql)

I'm currently trying to handle concurrent inserts correctly using MySQL, I'm basically doing the following: CREATE TABLE foo (id INT NOT NULL PRIMARY KEY) ENGINE=INNODB; CREATE TABLE bar (id INT NOT ...
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39 views

How to decide whether to enable MySQL query cache using InnoDB

How should the decision to enable / disable the MySQL query cache be made, on a server that uses just InnoDB tables. Say for example, if the cache is enabled, then how should the output of: SHOW ...
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25 views

MySQL CPU high usage

My MySQL service started to using a lot of CPU recently. Few second after restart it takes 100% CPU's. I tried already changing my.cnf file to optimize cache/buffers. I have no idea what causing that ...
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sql indexing and performance

I am using mysql5.1, i have table which has about 15 lakh (1.5 million) records.This table has records for different entities i.e child records for all master entities. There are 8 columns in this ...
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1answer
37 views

How to grant super privilege to the user?

I have created a user and given privileges to the user1. `grant all privileges on db1.* to user1@'%' with grant option; Am using mysql workbench to import dumps to my database. While importing ...
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1answer
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MySQL database stops working after log enabled

I have this strange issue. I have MySql workbench, which I use to write queries for MySQL database (xampp 3.2.1). Everything works fine, but recently I found myself having to profile the queries my ...
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Amazon rds MySql -> concurrent connections deadlocks

I normally hang around in StackOverflow but I think this issue is better suited here. I've built an application in C#.NET that uses MySql as a database. My application inserts and updates data in the ...
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MySQL - How to grant read access to all tables, write access to a few, to one user for multiple databases?

Ubuntu Server 11.04 - a testing server with at least 10 copies of the production code. Each copy has its own database. And there are two sets of database prefixes in operation. There is an add-on ...
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How to make MYSQL smart enough to understand when it should take into account stop word and when it shouldn't?

Ok, here is the problem. I have a table Text text nature .... text2 nature .... a lot of nature ... rows here.. .... go with nature with nature her go it Now, i select: select * From MyFullText ...
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Any idea why this seemingly-simple query is really slow?

Here's the query SELECT count(*) FROM registration r LEFT JOIN registration r2 ON r.baggage_group_id = r2.baggage_group_id AND r2.team_id IS NULL WHERE r.event_id = "102577"; It seems pretty ...
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29 views

Can't force mysql to use index

There are many similar questions about force index but mine is something different because i successfully use index at local dev server but can't on production server. I have a table with more than ...
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Can't Add Databases through PHPMyAdmin

EDIT (should've mentioned this sooner): I'm using a Mac, running OS X 10.9.2 Being fairly new to PHPMyAdmin, I thought I was removing settings/privileges for one single user through PHPMyAdmin, but ...
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Latitude and Longtitude Distance Calculation

I'm using MySQL and I am trying to calculate the distance in meters between two different longitude, latitude coordinates. I wrote a stored function in MySQL but it calculates just 1 for each row in ...
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?deactivate facebook for multi-site forcing reactivation site-wide? [closed]

I am connecting to a remote mysql database of my wordpress-website using SSH and mysql-workbench, and have found "key 32228 - facebook activated - wp_databasetab3_changes_tracker". Can I deactivate ...
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24 views

Check for table corruption

I monitor MySQL databases by querying various things remotely. I recently came across an issue where by a table had become corrupted but I did not know about it until the daily mysqldump failed. Is ...
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Problem with mysqldump and view

When using mysqldump to backup MySQL, I got following error. mysqldump --all-databases --routines >> all.sql mysqldump: Couldn't execute 'show table status like 'hdkien'': SELECT command denied ...
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How to stop the execution of a long running insert query?

I've executed an INSERT INTO ... SELECT as a job on my MySQL instance and then I realized that number of records that is selected by the WHERE condition is more than my patience. It's already taken 12 ...
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MySQL query using left join on two inline views not returning rows without values in second view

For some reason when I execute the code below I'm only getting results back that have sku in both views. I thought this should give me everything in the first view and add the content from the second ...
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1answer
52 views

Optimizing a slow MySQL query

I'm trying to optimize a ~100GB database. All data values are in one single innodb table, is this bad? Here's what a common query looks like: SELECT `CensorCode`, `LocalDateTime`, `UTCOffset`, ...
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23 views

Is it faster to load several small files, or one big file?

We have a 26GB file that we have to load into an empty table. I was curious, is it faster to load nine 3GB files or one 26GB file? Or is there no difference?
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What is a loose index scan?

I was reading that MySQL can not use an index on 2 range conditions due to not having a "loose index scan" What exactly does this mean? Is it related to the underlying or the implementation of the ...
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28 views

Fan-In replication 4 Master -> 1 slave

I am trying to merge 4 source db's (one for each region) into a global db. We use ID ranges as primary key on the tables in each region and so the merge should happen nicely. I have a fairly high ...
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Mysql Master Offline

In a unidirectional Master-Slave setup, should the slave be manually stopped in cases where the Master is offline due to Maintenance, Crash etc. ? Or should one just leave it so that it keeps trying ...
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What's the best way to translate a website [on hold]

I have a website in Django using MySQL, and I have more than 4.000 entries that I want to translate. What's the best way to do it? Create a new database for every language? Create other table for ...
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MariaDB Galera setup with drastically different amounts of memory used on cluster nodes - why?

We have a 3 node MariaDB Galera cluster. All nodes are identical and the config on each is identical. They have 64GB of RAM each. The output of the following query is 28: SELECT ...
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MySQL Query for combobox

I have two tables in my database.namely books and bookidofid. where bookidofid from books table is referenced to bookidofid from bookidofid table Table books ...
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Select different time

I looked on the internet and I found your post on the stackexchange. I will try to explain in more detail what we really need I do not know well to write English It is a system for airporttaxi id ...
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15 views

How to link a MySQL Table with a binary key into Access?

In MS Access I've created a linked table via ODBC to a MySQL table with a binary(16) primary key column (UUID). MS Access only shows the first row, all other rows have #deleted entries. I guess the ...
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25 views

How can I rewrite the following removing the date_format function?

I have a table with a column when that is of type datetime. I am doing the following filter which can not use and index: AND DATE_FORMAT(t1.when, '%Y-%m-%d') <= LAST_DAY(now() - interval 1 month ) ...
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What is the difference between uniqe index/unique/unique key/unique constraint keywords?

I am using mysql 5.5.16 What is the difference between the following DDL statements? 1) create table sql_query ( id int not null , query_text varchar(21826) not null , query_md5 ...
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Securing Your MySQL Server within your team?

Recently I have been having an issue with our internal team members changing the password of the root user. I noticed the following things: OLD_PASSWORD = 1 (So all passwords on our development ...
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How to use Select query just right after Insert on master in a query.?

I have a question on mysql replication. As usual, I deployed my db structure like the Update on master db, the select on slave. My questions. If I use SELECT query just right after INSERT in a query, ...
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MySQL Slave not updated

This might be a duplicate of questions on the same problem asked before. But all the suggestions to the previous questions do not seem to work in my case. I have set up Replication using SSH Tunnel. ...
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Fastest way to create local copy of live InnoDB MySQL database?

We have a MySQL database (InnoDB) on our live Ubuntu 12.04 server which has grown quite large (25gb+). Every month or so we need to copy this database to our development machines to work on locally. ...
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Why does MySQL randomly display my databases?

Using InnoDb for the tables, Zend installation that comes with MySQL on Windows. Basically what happens is that at each system startup (not MySQL) I get a random snapshot of my databases at some ...
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1answer
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Duplicate Data from two column

i have a table which has only two column one is pid(Photo ID) and another one is tid(Tag ID) +-------+---------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | ...
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Create previously created MySQL database without .sql file

I had a bad server crash in which I was able to restore my MySQL files, but I was unable to do a dump in order to get the .sql file. In other words, I have each individual part that was saved in the ...
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Impact of replication compression & encryption on performance, traffic?

What is the impact of MySQL compressed-slave-protocol on replication traffic? According to High performance MySQL it can lower the traffic to a third of the same replication without the compression. ...
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MySQL schema for recurring events - Query by specific date

I've just asked this exact same question on stackoverflow so apologies for cross posting but I only just noticed dba so thought I'd ask across here as well. I'm just about to start putting together a ...
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Space not reclaimed after dropping MyISAM table

I just dropped a rather large MyISAM table (~4 gb); it was 350k rows with about 11k of data per row. However, when I run df -h on my database server, I am still at 100% disk usage, so much so that I ...