All versions of MySQL (not Microsoft SQL Server). Please also add a version-specific tag like mysql-5.7 if that is relevant to the question.

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Many transactions are getting stuck in the “cleaning up” state - what could cause that?

I'm trying to track down a locking issue, and found via SHOW PROCESSLIST that when the queries in question are waiting for locks and timing out, there are no other queries active in the process list. ...
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2answers
410 views

Mysql fulltext index search returning weird result

I have ingredient table. I want all those recipes which have certain ingredients. Below is my table structure. Table(ingredient) - Applied fulltext index on ingredient column. ...
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125 views

return my.conf values to sane levels (total memory footprint = 220GB)

I recently took over administration responsibilities for one of our databases. The existing my.cnf has some crazy values. I should mention that one table has 1.8 billion rows of mostly unneeded ...
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3answers
1k views

Deleting data from a large table with replication

I need to delete all the rows from a given table. The table contains millions or records. The master database is being replicated to several slaves and I wish to do that without creating a replication ...
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2answers
901 views

Very high load avg for MySQL database [closed]

I have a backend server which response to my clients app, it has more than 20k~25k hit per second and this make my server load average very high, I believe that my MySQL config is not appropriate. In ...
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1answer
48 views

Do threads in cache still use memory?

I was studying about how and how much memory allocated to each connection thread and found below MySQL tutorial: http://dev.mysql.com/doc/refman/5.1/en/memory-use.html There is a point mentioned as ...
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1answer
481 views

MySQL backing up MyISAM tables by copying the physical files - and automating the process

I have 2 databases with MyISAM tables running on a Windows 2008 Server. These databases are about 20GB in size with a few tables with millions of rows. My question regards backing them up on a weekly ...
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2answers
265 views

Monthly report by time [closed]

I work in a parking company. We need a report of monthly vehicle exits by time. select hour(datetimeout) as 'dateout',count(*) from to_leaveveh where datetimeout between '2014-09-01' and ...
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2answers
254 views

Relational Model vs. Database Products [closed]

The formal Relational Model (logical level) for databases is not exactly the same thing as you get with MySQL, Oracle or other major products / implementations of ‘relational’ database management ...
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224 views

mysql information schema database last used datetime

I have a lot of tables in my database, almost 1,000. Most of them I am not using now. Is there any way to know from the information schema tables when I have last used my tables?
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183 views

Best practice for storing image order number in a database

I am designing a social networking website(mysql with InnoDB engine + php) where I need to store image sequence in a database. The table structure is as follows:- PicId (BIGINT, AUTO INCREMENT, PK) ...
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1answer
1k views

Multiple User Types - DB Design Advice

I'm developing a web application that will support user authentication with corresponding roles for each user. Also, my users can be of different types and have different fields associated with them. ...
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1answer
188 views

Adding time to an event that runs on a weekly basis

I have this event that runs every Thursday CREATE EVENT le_drop_database ON SCHEDULE EVERY 1 WEEK STARTS CURRENT_DATE + INTERVAL 3 - WEEKDAY(CURRENT_DATE) DAY DO BEGIN drop database carbon; ...
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1answer
1k views

Table is dropped but ibd file still exists

I was dropping some unwanted tables I have in the MySQL. When I run a drop table, its showing table doesnot exists. But when a check in the data directory, the .ibd file exists and its almost 1GB. How ...
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2answers
1k views

How to break table into two without losing performance?

According to http://stackoverflow.com/a/174047/14731, splitting away infrequently-needed columns frees up the cache allowing faster retrieval of the commonly-used columns. I've got a table whose ...
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1answer
284 views

MySQL configuration to connect to multiple local applications [closed]

I've installed FreeRADIUS, MySQL and FreeRADIUS management (a web-based app) on the same machine, with both FreeRADIUS and FreeRADIUS management using same user to connect MySQL. My problem is when I ...
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1answer
622 views

Fetch data from same table using two group by clauses in mysql

I have one table name as consultant with 4 fields(id, name,user_type, Created date). I need to write an mysql query for return the count of user_type in each month. In my table, user_type is ...
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3answers
3k views

mysql database restore takes long time

I am in the process of reinstalling a Ubuntu server to rhel6 server. I have a pretty huge database. When I checked the mysql data directory size, it was around 354 GB. However, I dumped the entire ...
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1answer
50 views

What is the generally accepted method and tools for profiling MySQL queries?

Profiling database queries is difficult, and dependent on database technology. In MySQL, what is the usual (or, in deference to that, a great) process for profiling a query? For example: Run the ...
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184 views

MySQL replication of single DB to same server

I have a DB Server running CentOS 6.4 and MySQL 5.5 from RPMs (not source). I have dozens of databases but one of them is being hit quite hard with large selects which locks out other updates which ...
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163 views

Significant difference between duration for querys in SHOW PROFILE and SHOW PROFILES?

I have use mysql profiler to optimize an opencart query which takes more than 10 seconds to executes. mysql> SHOW PROFILES; ...
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1answer
216 views

Slow queries InnoDB occasionaly

I have the next table: CREATE TABLE `sessions` ( `session_id` char(32) COLLATE utf8_unicode_ci NOT NULL, `session_expires` int(11) NOT NULL DEFAULT '0', `session_data` varchar(10000) COLLATE ...
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1answer
32 views

Is there any value in adding an already indexed column to a composite index?

The title says it all. Does the query optimizer see composite indexes where each column is already indexed as redundant? Or, is it used when each of the composite index's columns are in the WHERE ...
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1answer
642 views

InnoDB primary key efficiency

I've read a number of articles regarding efficiency of primary keys depending on the storage engine, and I am left confused. Given a simple many-to-many table with two fields, storeId and zoneId, ...
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2answers
215 views

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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2answers
267 views

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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1answer
163 views

Determining replication traffic

is there any way to determine from server statistics* running MySQL, how much traffic(bits per second) WOULD replication consume between 2 servers, without setting-up the actual replication between ...
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1answer
444 views

MySQL - Best long read query solution within a replication based system

I'm working on a project where work in a queue requires a database read against heterogeneous table schemas (InnoDB/MyISAM). The queries constructed during the "read" process can result in 10-15 ...
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1answer
706 views

When tables are locked does MySQL queue queries?

I have a small production website, but it's live 24/7. When running the Optimize, Analyze or Repair commands, MySQL locks the table it is working on. QUESTIONS How would this effect users trying ...
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1answer
4k views

MySQL: NOT EXISTS vs LEFT OUTER JOIN…IS NULL

Is NOT EXISTS or LEFT OUTER JOIN...IS NULL more efficient for finding records in one table that aren't in another? Specifically, I'm trying to figure out which of the two queries below is better: ...
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199 views

creating table result in errno 150

I'm trying to create the following schema, but I'm getting errors when I'm trying to create project and staffphone tables. Not sure what is it complaining about. mysql> CREATE TABLE staff( ...
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1answer
155 views

How does the transactions interact if you set a different isolation level per connection?

I read that I can have different isolation levels per connection and in the server. The default isolation level is REPEATABLE-READ. So if I have a transaction that issues a SERIALIZED to the client ...
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1answer
559 views

Native replication from Percona XtraDB Cluster to a standard stand-alone slave

I'm replicating from one node of a three-member Percona XtraDB cluster to a separate slave, using regular MySQL replication. The node is set to write binlog in ROW mode, with log_slave_updates=true ...
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3answers
871 views

What happens when we take a timediff between timestamp and datetime

Say I have following table in mysql (5.5+): CREATE TABLE IF NOT EXISTS `test` ( `id` int(11) NOT NULL, `x_time` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP, ...
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372 views

Missing rows in MyISAM tables with 10-20 billion records

I've got 2 tables with 10-20 billion records each. Currently these are in MyISAM (MySQL). They only require to be built and indexed once, after this only SELECT is used. They are currently ...
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mysql 5.6 GTID replication 'Got fatal error 1236 from master when reading data from binary log'

I Checked SHOW SLAVE STATUS error is "'Got fatal error 1236 from master when reading data from binary log: ''The slave is connecting using CHANGE MASTER TO MASTER_AUTO_POSITION = 1, but the master ...
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2answers
183 views

Is column order reliable in UPDATE?

Can we reply on the order of columns in an UPDATE? SET @x = 0 UPDATE table1 SET col1=IF(col1 IS NULL, NULL, @x:=@x+col1), col2=IF(col2 IS NULL, NULL, @x:=@x+col2), col3=IF(col3 IS NULL, NULL, @x:=0) ...
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1answer
91 views

Is an explicit KEY redundant if it is covered by a UNIQUE KEY?

I am auditing an application which I've been developing over the course of several weeks. I've noticed this in CREATE TABLE: UNIQUE KEY `baz_3` (`baz`,`foo`,`bar`), KEY `baz` (`baz`), Is the ...
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4answers
131 views

Amount of data in a database table

I am trying to run an alter query on a table, and its giving me a Lost connection to MySQL server during query MySQL server has gone away. The query that I am running is alter table table_name ...
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0answers
189 views

problem installing mytop , need a up to date tools for monitoring mysql

so i'm trying to installl mytop to monitor the database i'm following this instruction : http://www.sohailriaz.com/how-to-install-mytop-a-top-clone-for-mysql/ when i try to install it with yum i get ...
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1answer
409 views

MySQL auto_increment delivers different primary key in MyISAM and InnoDB

I have a table with auto incremental primary key. If I want to change a row and add new rows I got different primary keys depending on engine MyISAM and InnoDB. The original table is: pk.. ...
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2answers
1k views

multiple connections on MySQL database with no users on httpd

My database seems to have many open connections despite having no users on httpd. mysql> SHOW PROCESSLIST; ...
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1answer
4k views

filling a table by triggering multiple tables on insert

I have a table m contains the following fields: id int(11) not null auto_increment, //PK name varchar(100) null, something_else varchar(100) default 'not important' I need to fill up table m by ...
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2answers
659 views

How to create root user after running mysql_install_db?

I'm installing MySQL on ubuntu and I changed the data directory. I created new data files using mysql_install_db command. So now I need to access my database using root but it won't let me in. I ...
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4answers
252 views

Better Indexing for MySQL?

Is it better to index each column individually with it's own key or to index multiple columns under the primary key? I've seen it done both ways in many different applications and I don't see a clear ...
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0answers
219 views

mysql.sock missing

I started my MYSQL database this morning but failed. And I tried all means I can think of: chown -R mysql.mysql /var/lib/mysql chmod g+w /var/run/mysqld chgrp mysql /var/run/mysqld chmod -R 755 ...
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3k views

MySQL - ERROR 1045 (28000): Access denied for user : permission issue

ex :on first server : mysql> show grants for 'test'@'localhost'; +---------------------------------------------------+ | Grants for test@localhost | ...
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2answers
2k views

INT or TIMESTAMP for the change time column in a logging table?

We're having an argument over what to use for storing change date in a new log table for our site. One side says, use INT for the timestamp, storing the UNIX timestamp. We can convert the datetime ...
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1answer
3k views

MySQL dynamically optimize innodb tables without “file per table” setting

We are getting a “too many connections” error once a week the same time a mysql procedure runs. The procedure runs “optimize table” on hundreds of tables and takes nearly ten hours to finish, taking ...
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1answer
12k views

Delete from table where multiple fields match select subquery from other table

I want to delete an entry in a table where multiple fields match the results of another select subquery which takes data from another table. This is what I have so far, though it doesn't work: ...