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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3
votes
2answers
6k views

MySQL “server has gone away” using SQLyog

I'm trying to copy a database from a server to my local machine, I've installed Wamp 2.2, mysql 5.5.16, but during copying db I m getting "mysql server has gone" 2006, I've tried to fix it by changing ...
2
votes
3answers
4k views

Master-master Replication with 3 Nodes

I need to configure mysql master/master replication with 3 nodes. Currently I have master/slave setup and I need to move it to master/master with 3 nodes. I have gone through some posts about ...
2
votes
2answers
7k views

How to auto-refresh/re-run a query every few seconds?

I have a script running against a database with no GUI. This simple query lets me see its progress: select *, (select count(*) from domains) as count, (select 456976-count(*) from ...
2
votes
2answers
2k views

Percona XtraDB Cluster and MySQL Replication

I've setup a 3-node multi master replication with percona xtradb cluster, it works perfectly. Now I've tried to add some read-only slaves setting up replication as usual but it seems the binlog ...
2
votes
3answers
4k views

Deleting Data From Multiple Tables

Suppose,I've a table called UNIVERSITY containing universities name: universityID universityNAME isACTIVE 7 GNDU 1 6 PU 1 5 ...
2
votes
2answers
3k views

Best practices to secure mysql

I don't have that much knowledge about mysql and i would like to secure a MySQL server. We have a few VPS running around the world (6 currently) and they all need to store information in our mySQL ...
2
votes
3answers
3k views

Is it normal to use many Triggers?

I have many so-called summary columns throughout my database to count number of rows in other tables. For example, counting the number of comments by a user (a column in the user table). Currently, I ...
2
votes
3answers
2k views

What are the best practices for triggers to maintain a revision number on records?

I have an audit trail implemented on an application database that captures old value, new value, modification time, and user inserting it into another table. I'm now wanting to add a revision number ...
1
vote
2answers
591 views

RAID configuration for mysql

I attached 4 10G disks to mysql Server and I used RAID 0 but still same mysql performance the same, Do I have to change configuration in my.cnf to let mysql know about RAID 0. this is my mount ...
1
vote
3answers
3k 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 ...
1
vote
1answer
2k views

mysqlbinlog failing with “ ERROR 1032 (HY000) at line 48: Can't find record in `` ” Error

I am facing some issue with PITR restore using mysqlbinlog . It is failing with the following error . # mysqlbinlog mysql-bin.000035 | mysql -u root -p db Enter password: ERROR 1032 (HY000) at ...
1
vote
2answers
4k views

How to optimize MySQL for large BLOB updates

I have a table that holds large BLOBs (up to 10M), and is updated frequently. The problem is that UPDATE statements can take up to 1 second to execute, and due to app design this blocks UI. I need to ...
1
vote
3answers
1k views

MySQL InnoDB Sorting Issue

I was surprised to see MySQL's InnoDB showing an interesting behavior, which I cannot fully explain. According to the official MySQL InnoDB Documentation: "All indexes other than the clustered ...
1
vote
1answer
5k views

How to debug a db memory-leak causing mysql to go before it's own limits?

We are having a problem with one of the database server of one application, possibly caused by some code that is creating a problem in the way Mysql manage it's memory. Until the second week of ...
1
vote
1answer
2k views

Can putting mysql DB into memory or having the innodb_buffer_pool_size match the size of DB increase performance?

We have a mysql database that has roughly 80 gigabytes (GB) of data using inno_db engine. We are looking to increase performance on the database (we looked at the slow log and gone through and ...
1
vote
1answer
490 views

For 768M RAM server is 617M allocation in my.cnf good or bad?

I have a write-intensive web app, and I bought a VDS with 768M RAM Is this my.cnf good for my purposes? I specified bulk_insert_buffer_size to 126M and some other parameters as below: ...
0
votes
1answer
57 views

One to one vs One to many (syntax differences)

What is the syntax difference in MySQL between One to one and One to many? One to many looks like this: CREATE TABLE A( a1 int not null, a2 int, PRIMARY KEY (a1) ); CREATE TABLE B( b1 int not null, ...
0
votes
1answer
379 views

How can lots of ram (128 GB) be used to improve MySQL 5.5 index creation?

This is similar to another post of mine, but now I have a different table structure, and it's still unclear what MySQL parameters should be changed to take advantage of the extra ram my machine ...
16
votes
6answers
303 views

Securing DB passwords

Looking at the structure of most PHP/MySQL-based websites I've seen, it appears that it's not terribly difficult to discern the database password if you dig a bit, as there's invariably a setup or ...
13
votes
5answers
2k views

Infrastructure for Highly Concurrent, High Write DB

My requirements are: 3000 Connections 70-85% Write vs Read Currently, we are maxing out a High-CPU, Extra Large Instance at 700 connections. All 8 cores are maxed. We think it's the number of ...
10
votes
1answer
11k views

Error creating foreign key from MySQL Workbench

I'm trying to synchronize schema changes from MySQL Workbench to my database. I'm getting the following error when it tries to create a foreign key: Executing SQL script in server ERROR: Error 1005: ...
9
votes
1answer
5k views

How can I determine the size of a dump file prior to dumping?

How can I determine or estimate the size of the SQL dump file prior to using something like mysqldump?
9
votes
2answers
7k views

Monitor MySQL activity per database?

What is the best way to monitor activity on each database of my server ? I tried mtop/mytop which display activity in real time but aren't very practical to see all the queries executed on it. I ...
8
votes
2answers
423 views

Why would MySQL do serial synchronous I/O?

When looking at a particularly annoying query over MyISAM tables which takes a long time to execute on a number of occasions, I have noted that MySQL seems to expose a rather strange I/O pattern: when ...
8
votes
3answers
10k views

Is it better to separate a big query into multiple smaller queries?

There are situations which require having really big query joining several tables together with sub select statements in them to produce the desired results. My question is, should we consider ...
8
votes
2answers
17k views

Update many rows in a table with a single statement?

What is the easiest way to update many rows in a table? I have a csv file that looks like this: |primary_key |value| | 1 | xyz| | 2 | abc| | 3 | def| ... Rows with ...
8
votes
5answers
19k views

Can't connect to MySQL database over SSH with Workbench

I'm trying to connect to my database via SSH tunneling from one of our web app servers with MySQL Workbench. Here's the basic config; note that I changed some values in the screenshot for security ...
7
votes
1answer
6k views

How do you disable anonymous login? - MySQL

According to the MySQL documentation, you can harden a MySQL server by adding passwords, or removing the anonymous accounts. If you want to prevent clients from connecting as anonymous users ...
7
votes
1answer
5k views

Why does that query cause lock wait timeouts?

From time to time, I find a lot of these errors in my PHP error log: MYSQL.1213: Deadlock found when trying to get lock; try restarting transactionSQL The problem persists for about 2 or 3 minutes. ...
7
votes
1answer
15k views

Should a MySQL replication slave be set to read only?

I've got replication running on Percona Server 5.5 by following this guide and wondered if I should add read-only=1 to my slave's my.cnf to make it read only? The guide sets up replication for the ...
7
votes
1answer
2k views

recover a single mysql database on a busy master-slave replicated system

Looking for a strategy or tool to deal with recovering a single database to a point-in-time in a busy replicated system. I have 12 databases running on 2 MySQL 5.0.77 servers in master-slave ...
7
votes
4answers
5k views

Incomplete mysqldump

I'm trying to run mysqldump to create a database snapshot, and I'm finding it will randomly stop midway, without reporting any error. My database is relatively small (about 100MB) and is using InnoDB. ...
7
votes
1answer
729 views

Application Settings in Database

In the past I have stored all generic settings and configuration items such as: custom application title, home address, version, debug, etc.. all in a "settings.php" file that I would include into all ...
7
votes
1answer
513 views

Dealing with temp tables when I have not control over db variables

I have no control over things like tmp_table_size and max_heap_table_size, and so as our tables grow the time taken by queries requiring temp tables is growing geometrically. I am wondering if there ...
7
votes
6answers
1k views

Alternative Database Tools for Web Admin [closed]

I currently use phpmyadmin for most of my database administration. It works well enough, but I'm interested in other tools that might work more quickly/efficiently/etc... What are the best and/or ...
6
votes
1answer
1k views

Install MySQL for Windows from .zip and reset root password

I wanted to have on my PC (with Windows 8.1 x64) the MySQL server only, without Workbench or something. So I downloaded .zip archive from dev.mysql.com/downloads. It's a download for Win64 on x86_64 ...
6
votes
1answer
10k views

UPDATE table based on the same table

I have a table with product descriptions, and each product description has a product_id and a language_id. What I want to do is update all of the fields with a language_id of 2 to be equal to the same ...
6
votes
4answers
16k views

How to increase fast backup and restore of 500GB database using mysqldump?

There is a database A size of 500GB. Tables in database A contains both MyISAM and INNODB tables. MyISAM tables are master tables and Innodb tables are main transaction tables. Backup and restore ...
6
votes
2answers
2k views

Amazon RDS I/O requests - 1 query = 1 billable I/O?

I have an InnoDB database that I'd like to migrate onto Amazon RDS. My current implementation, hosted on my own server, shows roughly 8M queries per month. The RDS site say that I/O Rate $0.10 ...
6
votes
2answers
26k views

How to log verbose output from mysqldump?

You typically save the verbose output of a Linux command like this: # command > output.txt But when you use a command like mysqldump, the > option outputs the dump of the database tables to ...
6
votes
2answers
596 views

Estimating distribution of row access in mysql

I am trying to get an idea of the size of the "hot data" part of a rather large table, and I was wondering if this could be done directly in mysql. I know that with the percona version of mysql, I can ...
6
votes
1answer
1k views

How can I get status messages during a large re-indexing operation with MySQL 5.5?

I get large data transfers periodically that I used to completely replace the contents of a MySQL table. Each time I do this, I truncate the table, disable keys, add several million rows of data, and ...
5
votes
2answers
7k views

ERROR 1054 (42S22): Unknown column 'plugin' in 'mysql.user'

I am trying to grant privileges for a user to a new database mysql> grant all on db_test.* to 'user_test'@'localhost' identified by 'usersexistingpassword'; I get the following error ERROR 1054 ...
5
votes
1answer
269 views

Does MySQL exectution plan depend on available indexes?

Does MySQL choose an execution plan for a given query taking into account what indexes are available, or does it first choose an execution plan and then uses indexes if they are available? ...
5
votes
1answer
3k views

What are the drawbacks of using Galera Cluster instead of Master/Slave Replication?

What are the drawbacks of using Galera Cluster instead of regular Master/Slave Replication? Galera's 0 slave lag time, Synchronous replication and no Single point of failure seem very appealing then ...
5
votes
1answer
2k views

Possibilities to speed up InnoDB INSERTs and UPDATEs

My website retains user sessions in an innodb table. This usually works well, but a few hundred times a day, the INSERT and particularly the UPDATE statements run slower. I'm monitoring when, and it ...
5
votes
4answers
3k views

Slave SQL thread got hanged

We have a master - slave setup with ROW based replication. We are seeing huge delay's on the salve even though there is no activity running wither on master or slave. When we looked in, we observed ...
5
votes
1answer
10k views

SELECT LIMIT 1 per column value?

Lets say I have the following table ----------------------------- | user_id | comment | ----------------------------- | 2 | thats cool | | 2 | awesome | | 3 | ...
5
votes
1answer
2k views

Mysql sub query returns more than 1 row

SELECT * FROM wp_posts WHERE ID IN ( (SELECT courses FROM wp_category WHERE CatID =401) OR (SELECT meta_value FROM wp_postmeta WHERE post_id IN (SELECT courses FROM wp_category WHERE CatID =401) ...
5
votes
1answer
1k views

MySQL Import CSV with Multiple Field Separators

I'm trying to import this CSV file into MySQL that appears to be optionally enclosed by more than one character. Unfortunately, MySQL only supports one character as a field separator. I am stuck ...