Questions tagged [mysql]

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
2answers
5k views

MySQL Slow Query Log - SELECT /*!N SQL_NO_CACHE */

Using mysqldumpslow, I can see that the most common entries in a MySQL slow query log are of the following form: SELECT /*!N SQL_NO_CACHE */ from wp_posts (or wp_comments). I can't seem to find much ...
5
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1answer
38k views

How do I open a MySQL Database Dump?

I work for a doctor's office, and we are in the process of switching EMR systems. The previous system has provided a physical 'dump' of the database. I however, don't know how to open this database ...
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3answers
1k views

Best architecture solution for heavy data mining system, that can run on cloud

We are currently hosting our MySQL database on a dedicated server with lots of memory and processors. We would like to push it to a different architecture that would allow us to scale it easily, ...
4
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3answers
2k views

MySQL very slow query when changing one WHERE field despite no index/key

This is quite a confusing issue for me. I have a database full of baseball statistics. Running this query: SELECT * FROM hits JOIN stadiums ON stadiums.gameName = hits.gameName JOIN players ON (...
6
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2answers
8k views

What is the point of the TABLE_CATALOG column in INFORMATION_SCHEMA.TABLES?

In MySQL's table INFORMATION_SCHEMA.TABLES, there's a column named 'TABLE_CATALOG'. The documentation is sparse on this column and I'm wondering what the heck is the purpose of this? Any killer-app ...
16
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3answers
15k views

ALTER TABLE on a large table with an indexed column

I have a large table with a VARCHAR(20) column, and I need to modify that to become a VARCHAR(50) column. Typically, performing an ALTER TABLE (adding a TINYINT) on this particular table takes about ...
1
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2answers
4k views

Distributed Transactions between SQL Server 2000 & MySQL Stopped Working

We have been successfully copying data from a MySQL Slave database into a SQL Server 2000 database. The MySQL server is a linked server. I have tried using v3.51 and v5.1.8 of the ODBC connector ...
3
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2answers
2k views

Testing Query Speed

When I'm running a query for the first time, it takes x miliseconds to be executed. When I run it the second time it takes a lot less time. I assume that it is some caching involved in this mechanism, ...
3
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1answer
3k views

Suggest a MySQL book for me [closed]

I have recently joined a team in my corp office that has mysql as a part of their work profile. Though the mysql work not often in this team, but when they do it comes in big scale. The main mysql ...
8
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9answers
4k views

Which DBMS are fast enough for an online game (few thousand players)? [closed]

I'm currently making an MMORPG game, which could have a few thousand players online at the same time (probably not; just wishful thinking). First we wanted to use MySQL, but I have heard it isn't fast ...
4
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2answers
10k views

Can't connect to MySQL DB

I've been trying to install Apache because I want to do PHP development work. The install didn't work so I aborted it and wanted to make sure that my other installs using MySQL were still working. I ...
6
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1answer
621 views

MySQL Replication: Insert generating VERY huge temporary tables

our replication slave is generating ~300GB temporary files while running relatively simple inserts. Our setup: Master: 5.0.45-0.sles10.x86_64, Slave: 5.0.85-win32, also tried with 5.1.57-win64, ...
6
votes
1answer
730 views

How can I create and initialize a schema for a embedded MySQL DB?

I want to create an embedded MySQL database for running tests, but I'm not sure how to do it. How do I initialize the database? How do I run my create table statements? I'm using Perl, so it needs ...
10
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3answers
10k views

Query problem: there can be only one auto column

Can someone please tell me what's wrong with this table definition. mysql version is 5.1.52-log root@localhost spoolrdb> create table spoolqueue ( queue int, ...
9
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3answers
6k views

query regarding combining an update and an insert query into a single query in mysql

i want to track history of changes for a user, so that whenever he changes his profile, i need to take the old data and store in history and update with new data. I can use a select to get the old ...
14
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3answers
33k views

How do I output MySQL logs to syslog?

I want to use syslog for logging MySQL(5.1.41) on Ubuntu(10.04 LTS). I found information that output error log to syslog. [mysqld_safe] syslog But I want to use syslog for logging general logs and ...
9
votes
1answer
11k views

Benefits of running the OPTIMIZE TABLE Query in MySQL DB Server

I would like to know what are the benefits [really practical] that can be reaped by running the OPTIMIZE TABLE tbl_name query in MySQL Server. I checked this once and found that after this is run, ...
5
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4answers
15k views

Storing arrays of integers in database (for efficient select)

I am creating a database that will store 100.000 (and probably more in the future) users. While this obviously happens in a table with 1 row per user, every user can (and will) store hundreds of items....
48
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19answers
212k views

Trying to use MySQL Workbench with TCP/IP over SSH - failed to connect

I can't connect using TCP/IP over SSH connection in MySQL Workbench from a PC. What's going on? I created a MySQL 5.1 database on an Ubuntu server mysql.myhost.com. I can access it locally. MySQL ...
2
votes
2answers
19k views

store result set in temporary table, variable or separate variables within a trigger

I'm in the process of creating some triggers to store the the average rating for a given product on the product table. I've also been asked to store the total number of reviews for the product. So - I ...
10
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4answers
33k views

MySQL: Why is auto_increment limited to just primary keys?

I know MySQL limits auto_increment columns to primary keys. Why is this? My first thought is that it's a performance restriction, since there probably is some counter table somewhere that must be ...
2
votes
1answer
916 views

Lost tables in Drupal site database

I have Drupal site on my local server build using pressflow I had problems with the xammp 1.7.4 server, so I delete everything except mysql and htdocs folders. I installed the server again, but the ...
16
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3answers
10k views

From where does the MySQL Query Optimizer read index statistics?

I'm trying to determine from where the MySQL optimizer obtains the list of indexes that are available for a table when it estimates the cost of (prepares) a query from.
8
votes
3answers
7k views

Using MySQL triggers or transactions?

I want to ask your opinion in using MySQL triggers or transactions in a website. Actually I have a history payment table with - UserId | OperationId | Comment | Credits | Sign (debit or credit). So ...
27
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2answers
9k views

How do I properly perform a MySQL bake-off?

I want to performance test (aka bake-off) MySQL server rpm against some other forks such as Percona server, MariaDB, and possibly some others. I'm hoping that by asking this question I can better ...
5
votes
1answer
1k views

What are your use-cases for HandlerSocket?

There's a bit of hype around: HandlerSocket It seems like faster, nosql access to MySQL data is becoming more desirable. Percona Server is now shipping with HandlerSocket built in. My question is, ...
11
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1answer
6k views

What is the difference between XtraBackup and rsync?

Yes, I'm going to run strace on them both... However, I would like to know ... What is XtraBackup is doing over and above rsync -ac src dest ? What's so special about XtraBbackup ? How is XtraBackup ...
6
votes
4answers
2k views

Would it be sensible to create a MySQL user for each user account of a web application?

The thought occurred to me recently, but I have a suspicion the idea might be insane. A couple of benefits I'm perceiving are: facilitate automated logging via triggers control mysql connections on a ...
5
votes
1answer
808 views

Speeding SQL queries for a large(?) WordPress database?

I am using a WordPress plugin called feedwordpress in order to run a planet like website (it takes content from other websites, with their permission) on WordPress (See it here). The plugin is great ...
14
votes
1answer
18k views

How is INFORMATION_SCHEMA implemented in MySQL?

The INFORMATION_SCHEMA is, in theory, a set of views specified in the SQL standard that allow the user to inspect the system's metadata. How is it this implemented in MySQL? When I connect to a fresh ...
3
votes
4answers
6k views

Connect to a remote MySQL Server from a dynamic IP address

My ISP at home uses a dynamic IP address. I'm trying to access a MySQL database at work. How can I connect to it (using MySQL Workbench)? I could grant all privileges to % so that any IP address will ...
16
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2answers
9k views

Reasons for occasionally slow queries?

We are running MySQL 5.1 on Windows Server 2008 R2. We have been doing some diagnostics on our database of late and have found some disturbing artifacts which we can't explain. We added some code to ...
5
votes
2answers
11k views

Creating and editing my.cnf by MySQL Workbench?

I just installed MySQL Server and MySQL Workbench on a clean Snow Leopard MacBook. I hooked up Workbench with the server and was able to start the MySQL Server from within the Workbench. I enter the ...
4
votes
4answers
548 views

How to get a column A which has the smaller column B grouping by column C?

I'd like to get the ID of a dataset for each category (my grouping column) which has the smallest "order" column. Here a set of data to explain my thoughts: CREATE TABLE DATAS ( ID INT(2) , ...
6
votes
2answers
854 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 ...
4
votes
1answer
626 views

Mysql fulltext boolean ignore phrase

I'm trying to come up with a mysql boolean search that matches "monkey" but ignores / doesn't take into account any matches of "monkey business". Something like the following is the general idea but ...
12
votes
2answers
6k views

Will these two queries result in a deadlock if executed in sequence?

This is almost certainly the cause of my other question, but I thought it was worth separating the two as I have a hypothesis based on the following log that I would love to have falsified or verified....
42
votes
5answers
77k views

How to SELECT from SHOW TABLE STATUS results

I'd like to limit the rows and columns that come back from the SHOW TABLE STATUS command in MySQL 5.1. Is there a way to get this same information through a SELECT statement so I can manipulate ...
7
votes
2answers
290 views

How should I Optimize storage for this table?

I'm using MySql to store a basic table of this format: id int(11) //Auto-Incrementing ID data varchar(5120) //Random input data, compressed by a program, not mysql. ---...
6
votes
1answer
2k 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 ...
17
votes
2answers
7k views

Trouble deciphering a deadlock in an innodb status log

We are accessing MySQL from the Microsoft ADO.NET connector. Occasionally we are seeing the following deadlock in our innodb status and haven't been able to identify the cause of the problem. It ...
3
votes
1answer
339 views

MySQL Replication not working properly on Ubuntu Lucid Lynx Server

I have two Linux boxes. On the master following is the configuration file (my.cnf) log-bin = master-bin log-bin-index = master-bin.index binlog-do-db = test_db server-id = 1 master status ...
10
votes
2answers
16k views

MySQL 5.1 InnoDB Configuration / 24GB RAM - bi-xeon high load

i'm running a facebook app which currently has 300 - 600 concurrent users (and growing). To get the hardware ready for growing i changed my i7 / 12gb ram / 2x 80gb intel x25 ssd's (debian 5.0 / mysql ...
8
votes
2answers
14k views

Mail alert from MySQL when databases are edited

How do I get mail from MySQL when root or someone else edits or updates a particular database? It should trigger sending a mail and log the edits. I have tried Triggers but its not working. Server ...
22
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6answers
57k views

Need to migrate SQL Server to MySQL

I have a database on SQL Server 2008 on a Windows server and I want to move all of the data to a MySQL database on a Ubuntu server. I have tried using the SQL Server Import and Export Wizard with the ...
4
votes
2answers
3k views

MySQL Replication Lag Behaving Erraticly

I've got a vanilla MySQL replication, using "MIXED" mode. The mysql slave lag calculation behaves very strangely - one moment it is 0 and the one after it it's 3630 seconds (or a similar number), ...
18
votes
2answers
3k views

What can we do in MySQL 5.0 Replication to address bandwidth concerns?

I am developing an application to run on the client PC (Win) which is configured with a MySQL server 5.1 instance that will act as read-only slave to the remote master. The remote master has dozens of ...
4
votes
2answers
4k views

How do you copy a table from MySqlServer_A to MySqlServer_B?

I have a daily task that collects data from 3 MySql Servers and then pushes that aggregate data back out to each of the servers deleting the previous days data. All servers are MySql. I would like to ...
7
votes
2answers
3k views

MySQL connection doesn't work anymore

I had two MySQL servers running (127.0.0.1:3306 and 127.0.0.1:3307). Now I get this strange error: mysql_connect(): Lost connection to MySQL server at 'reading initial communication packet' I can ...
22
votes
1answer
17k views

Does mysqldump export indices, by default?

I played around a little with mysqldump and I was wondering, if it does export indices (FULLTEXT, INDEX,...) by default. I read up on it and I found this option: --disable-keys, -K which suggests, ...

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