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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6
votes
5answers
17k 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 ...
6
votes
4answers
4k 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. ...
6
votes
3answers
4k views

Too Many Connections

I'm using MATLAB to feed the database but after a time I'm getting a too many connections error. I always using opendb and closedb in pair. Is it to fast the feeding? Do I have to wait after I ...
6
votes
1answer
503 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 ...
6
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 ...
5
votes
1answer
190 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
642 views

Is it Possible to Recover Data from a BLACKHOLE table? [closed]

I had created table with engine BLACKHOLE basically the BLACKHOLE storage engine acts as a “black hole” that accepts data but throws it away and does not store it. Retrievals always return an empty ...
5
votes
3answers
2k views

Storing a Shipping Address Best Practice

I'm building a checkout system which needs to store the customer's shipping address in the database and am unsure the best way to go about it. Currently I have an addresses table which stores each ...
5
votes
1answer
2k 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
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. ...
5
votes
5answers
15k 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 ...
5
votes
2answers
3k views

Large files in wamp\bin\mysql\mysql5.5.24\data directory

I have discovered these files located in the wamp\bin\mysql\mysql5.5.24\data folder on my Windows 2008 server. They are consuming about 22 GB on a 40 GB drive. I am using a LMS called moodle, that ...
5
votes
1answer
9k 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 ...
5
votes
4answers
3k views

How can I speed up “show columns” on MySQL?

My application depends on running "show columns" for certain tables. It takes about 60ms to run, whereas all our other queries take under a ms. Querying information_schema directly is even slower. ...
5
votes
3answers
2k views

CPU usage on RDS instance monotonically increasing with no change to query volume

I have two RDS instances: a R/W master and a read-only replica. On 29th June, the replica stopped registering replication data - not sure if this is related. On July 3rd, the master's CPU usage ...
5
votes
1answer
6k views

How can I find who holds the lock based on the hex-dumped?

I've been reading the Diagnosing MySQL InnoDB Locks article. Karl E. Jørgensen writes on 2008 so I'm consfusing it is in effect. I would like to supply a snippet of the SHOW ENGINE INNODB STATUS: ...
5
votes
1answer
3k views

Find out MySQL index size for a concrete index

In MySQL, for InnoDB engine, how do I find out the size of one of the indexes I have in the same table ? I know I can select the index_length from information_schema.tables, but this gives the total ...
5
votes
2answers
38k views

Grant table privileges to a user connecting from any host

I have a user account - let's call it 'wordpress' - that I need to allow to access a few catalog tables in another e-commerce database on the same server. I've configured the user with three host ...
5
votes
1answer
787 views

Database as a service (DbaaS) over dimensions--performance, scalability, & reliability?

MySql Database as a service: Amazon Xeround Another eg. PostgreSQL Database-as-a-Service. You can get the list of similar products here. Does anyone have details on their performance, ...
5
votes
2answers
573 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 ...
5
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
3answers
11k views

Resolving issue with mysql.proc after upgrading MySQL from 5.0.* to 5.1.*

Like many others, we upgraded our instance of MySQL from 5.0.* to 5.1.49. Since then, we've been running into an error that repeats itself when we perform certain actions: Attempting to view or run ...
4
votes
3answers
133 views

Queries hung for no specific reason

I'm having a strange issues for the past few days. I run data updates at night that shouldn't take more than a few hours. Several weeks ago a single script took two days to complete. I ran it again ...
4
votes
2answers
309 views

Best way to design a database and table to keep records of changes?

I need to setup a history feature on a project to keep track of prior changes. Let's say I have two tables right now: NOTES TABLE (id, userid, submissionid, message) SUBMISSIONS TABLE (id, name, ...
4
votes
2answers
5k 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 ...
4
votes
3answers
7k views

get all dates in the current month

i have a query in MySQL which serves me very well by getting all the records within the current month; SELECT date_field,val FROM MY_TABLE WHERE date_field>=(CURDATE()-INTERVAL 1 MONTH); The ...
4
votes
2answers
1k views

How to speed up mysql export and import

I need to perform a DB migration from Server A to Server B. Server A: MySQL version installed 5.0.6 Server B: MySQL version installed 5.6.20 OS: Both are running RedHat Linux 64bit. 16 ...
4
votes
1answer
1k views

Which are the minimum privileges required to get a backup of a MySQL database schema?

Which are the minimum privileges required to get a backup of a MySQL database schema? I am interested only on the schema, not on the data. Are SELECT privileges required?
4
votes
1answer
6k views

Reloading MySQL my.cnf changes

Do you have to restart MySQL to edit changes? Or can you edit them on the fly and restart MySQL or make the changes inside MySQL? This server runs 100s of website that are active and I don't really ...
4
votes
4answers
2k views

Why would I use the MySQL “system” command?

What can I do with the MySQL client's system command? Why does it exist? The most productive use I've seen is to look around the file system (e.g., to remember the file name you want to SOURCE or ...
4
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 ...
4
votes
1answer
2k views

How do uninitialized variables differ from NULL in Mysql?

Related, please read first for context: MySQL stored procedure: loop through table, delete rows. Logic problem: won't exit loop because of LIMIT option in query I think this is really ...
4
votes
1answer
10k views

how to retrieve rows of different dates using IN clause

My table structure: +-----------------+--------------+------+-----+-------------------+----------------+ | Field | Type | Null | Key | Default | Extra | ...
4
votes
1answer
681 views

How to Update same table on deletion in MYSQL?

In my Database I have a table: Employee with recursive association, an employee can be boss of other employee. Following is query I used to create table: CREATE TABLE IF NOT EXISTS `Employee` ...
4
votes
1answer
4k views

Is Percona xtrabackup the right choice for my 500GB MySQL backup?

I have a MySQL db with 500GB, consisting mainly of Innodb tables, and one big (200GB) MyISAM table. My current backup strategy is copying the db files to an external harddrive. This causes a downtime ...
4
votes
1answer
3k views

Setting up replication for MyISAM tables?

Before setting up a replication within MySQL, the data first needs to be transferred to the slave. Since MyISAM tables can be copied as files. Would it be okay to copy MyISAM files, .myd .myi .frm, ...
4
votes
3answers
2k views

How can I write a proper query to JOIN all of these tables without duplicates?

Let's say I have four tables: TABLE: players COLUMNS: id, first_name, last_name TABLE: passing_stats COLUMNS: id, year, passing_yards (several other passing columns) TABLE: rushing_stats ...
4
votes
1answer
668 views

How do I replicate Mysql DB server to new server?

Let me give you a preface by stating I am fairly new in Mysql environment. I am trying to replicate my production server to a new server (with better hardware configuration). I want to replicate ...
4
votes
2answers
2k views

Can a trigger access the query string?

I'm thinking about using triggers as a logging mechanism in MySQL (v. 5.1) and therefore I'd like my trigger to get the query string in order to store it in another tabe. I couldn't find anything ...
4
votes
2answers
4k views

How to convert mysql database charset to utf-8

I have a vb forum with a huge amount of data I need a way to convert this forum database tables charset with thier data from latin1_swedish_ci to utf8-general-ci How to do this ?
4
votes
1answer
4k views

Rebooting a MySQL Replication Slave

For the first time since it was set up I need to reboot a read-only MySQL replication slave. I found this article about downing a slave for maintenance (albeit he's just describing stopping the mysql ...
4
votes
3answers
727 views

Is Oracle DB immune to the InnoDB deadlocks found in MySQL?

It seems odd to me that MySQL would not handle this internally: "Deadlock found when trying to get lock; try restarting transaction" Does Oracle DB work around this issue? After all, Oracle owns ...
4
votes
2answers
684 views

More table or more database for better performance?

Lets say 1 website need 10 database table to work and i want a database pool that 40.000+ website will be inside. Which option is better for server performance? 1) 400 databases each have 1000 ...
3
votes
1answer
62 views

What's the best way to store and search through many product specifications

Let's say I have a lot of products and all of those products have a lot of specifications. These specifications can change at any time (e.g. "colour" could suddenly be available for new products) and ...
3
votes
2answers
297 views

How to get the sum of a particular item id in a column [closed]

Item ItemName PackageID Specifics brandname GRNQty UnitPric GRNValue 102814742801 ALL BRAN FLAKES 1PKT Bran. KELLOGS 7 15.9 111.3 102814742801 ALL BRAN ...
3
votes
1answer
8k views

Set value of character_set_client to utf8mb4

I'm trying to convert my DB to utf8mb4 by following this guide. I have set: [client] default-character-set = utf8mb4 [mysql] default-character-set = utf8mb4 [mysqld] init-connect='SET NAMES ...
3
votes
1answer
743 views

MySQL/MariaDB stored procedure compiles with typos

I just asked a similar question to this, but that turned out to be because MySQL column names are case insenstive and I was creating an ambiguity. I took the advice given and prefixed all my params ...