MySQL : Open-Source, Relational Database Management System

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Dealing with Multiple User Roles

I'm working on a project based on a CMS, where there is a built-in roles table. However, the CMS allows a user to have one role only using role_id And these are the requirements that struggling me: ...
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Why does this MySQL date_sub statement return wrong values?

I had a complex statement that was returning strange values and I traced it to the following line: SELECT id, updated FROM status WHERE updated > date_sub(NOW(), INTERVAL 6 MINUTE) ORDER BY ...
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“Temporary file write failure” when trying to change primary key in MySQL

In MySQL, When I trying to change primary key by this query: ALTER TABLE `resources` DROP PRIMARY KEY, ADD PRIMARY KEY (`role_id`, `category_id`, `lang`, `model`, `rule`); I execute this query ...
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Ordering a sequence of INSERT…SELECT statements to avoid a deadlock

I have the following two tables in a MySQL database: CREATE TABLE `names` ( `id` bigint(20) unsigned NOT NULL AUTO_INCREMENT, `name` varchar(60) NOT NULL, PRIMARY KEY (`id`), UNIQUE KEY ...
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Modulus calculation for compound primary keys in MySQL Cluster (and other sharded databases)

In MySQL Cluster, and generally in sharded databases, how is a compound primary key's modulus calculated? Say, for example, there are two tables that have primary keys like so: CREATE TABLE Orders ...
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Corrupted Filesystem: Possible to restore databases from the contents of /var/lib/mysql?

Using CentOS 6.4 x64. Not sure what happened but somehow my VPS filesystem got corrupted and it is now in a permanent read-only state. I've been working with my hosting provider's sys. admin. but ...
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64 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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How to update all primary keys in the existing database

I'm moving mysql multi-master replication to production using tungsten. I had setup the auto increment and offset values in my.cnf file. To achieve this i'll have to update my all primary keys of all ...
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Need help in optimizing a Slow Query

I am using userpoints module to provide points for different actions that they do on my site. mysql> desc userpoints; +-------------+---------+------+-----+---------+----------------+ | Field ...
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Querying number of tries since last successful log, checking IP as well as user

I asked this question before on stackoverflow, but it might fit better here, since it is mainly about database performance. The actual question With performance in mind, how would you go about ...
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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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MySQL dump error (#1005 - Can't create table 'novephp_cz_bv.jos_jquarks_customsets' (errno: 150))

I´m trying dump mysql database from MySQL 5.1. to MySQL 5.5. But I´m getting an error "#1005 - Can't create table 'novephp_cz_bv.jos_jquarks_customsets' (errno: 150)". Problematic part of script is ...
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Getting upcoming world wide releases from a database

From my database I want to get upcoming world wide release dates for an itemId along with the platformIds. If I have a table that looks like this and the current date is 2014-05-14 ...
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251 views

How to generate data for News Feed efficiently like facebook , googleplus , twitter e.t.c?

I have created table as post ( post_id int(15) auto_increment primary key , user_id int(11) , post_text varchar(2000) , post_type int(1), ...
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MySQL: Slow Update Queries

Our database server hangs for exactly 30 seconds on random UPDATE queries. It doesn't matter what field type the query is updating, it just seems like random selection. There are a few applications ...
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Why doesn't this query limit results by first and last name?

I have an ugly query, horrible table names courtesy of MySQL Workbench, and a severe lack of planning on my part to change to less verbose names prior to actually writing the code. Try to move past ...
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MySQL server taking up 100% CPU

I'm managing a site that does streaming video, the site is running off: Intel(R) Xeon(R) CPU E31220 @ 3.10GHz 16 GB RAM 2 x 2TB RAID1 1gbit unmetered bandwidth is not an issue as the ...
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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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Table already exists error when trying to import sql file

I am trying to upload a backup sql file through phpMyAdmin. I create the empty db with the same db name as in my import file in phpMyAdmin then use the import function selected from within this empty ...
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110 views

MULTIPLE INSERT VALUES with INSERT into another table

here a scenario to have a more clear picture. The DB is MySQL. I've 2 tables events and *event_users* : EVENTS id int type int date date time time ... EVENT_USERS event_id ...
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108 views

Best database for fast read all in one table

I currently have a large database in SQLite that I was using for rapid-prototyping for a software I am working on. Now that I am planning to move it to another database that should give better ...
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44 views

Move all InnoDB databases into one subdirectory (innodb_file_per_table is ON)

First of all, excuse my English. I want to run a MySQL 5.6 on ZFS volume, and need to move all InnoDB databases to one subdirectory (which in fact will be a different ZFS filesystem). For example, by ...
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Is it possible for unique key to break master-master replication in mysql?

I have a master-master mysql setup with 2 servers running the exact same application making writes to such a table: CREATE TABLE `metric` ( `id` bigint(20) unsigned NOT NULL AUTO_INCREMENT, ...
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120 views

What do spikes in InnoDB lock structures indicate?

I co-maintain a high traffic site similar to StackExchange. It runs MySQL 5.1 (working on replacing it with MySQL 5.5 or MariaDB). All our tables are InnoDB. MySQL goes down a couple of times a day. ...
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“dynamic set” in a MySQL table

I have a table where one column will have a few values many times (maybe 20 different values). Now I would like to use something like the set to improve performance and memory consumption. The problem ...
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Solved Mysql connection lost with HAProxy

I have master-master replication with mysql. and haproxy configured front of my master-master replication. When I connect my replication via HaProxy, mysql says that "MYSQL has gone away". But when I ...
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Master and slave tables with different character sets - will replication break?

We have some huge tables in our MySQL 5.6 database that have latin-1 as their character set, and want to convert them all to UTF-8 (along with converting the database's global character set). The ...
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Distribute records on different MySQL databases - MySQL Proxy alternative

My scenario is the following: Right now I am using one big MySQL database with multiple tables to store user data. Many tables contain auto increment columns. I would like to split this into 2 or ...
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Tagged questions

I have similar to StackExchange network that utilises tagged questions. In my web application Users also can find questions by tags. The query below returns a set of tagged questions: SELECT ...
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MySQL: Upgraded from 5.1 to 5.6 - no problem?

We're using Yum to maintain MySQL and our MySQL server only hosts a largish Drupal database. We recently upgraded via Yum from 5.1 to 5.6. The process went like so: Ran a mysqldump --all-databases ...
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51 views

crossplatform mysql_install_db script in mysql 5.5.34 on Windows

I downloaded mysql-5.5.34-win32.zip and found out there is mysql_install_db.pl script. However mysql 5.5 documentation says: mysql_install_db is a shell script and is available only on Unix ...
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Upgrading from MySQL 5.5 to 5.6 - timestamp issue?

I'm looking at upgrading my Percona Server setup from 5.5 to 5.6. Reading the upgrade docs from MySQL sounds mostly straightforward except for anything involving time/date columns. As far as I can ...
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restore using mysqlbinlog failing

While doing restore from a MySQL binary log file, it is failing with the following error . mysqlbinlog mysql-bin.000036 | mysql -u root -p asdb ERROR 1032 (HY000) at line 48: Can't find record in ...
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367 views

USING to join multiple tables with same field

I have 4 tables, each with a common field QuestionnaireId. I am wondering if there is any difference in output or performance difference between using USING on the field in each join or by specifying ...
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mysql query doesn't work inside a stored procedure

this is my stored procedure: CREATE DEFINER=`root`@`localhost` PROCEDURE `isUserValid`(IN `facebookId` VARCHAR(20), IN `userAccessToken` TEXT) NO SQL COMMENT 'check if user is valid. return ...
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How to set selinux permission for non-standard mysql bin log path?

By default, mysql bin log works in folder /var/log/mysql. but moving to any other share such /mylogs/mysql gives permission error. Below is the exact message: usr/sbin/mysqld: File ...
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mysql database is corrupt after system power failure

I have mysql database using xampp in my widows system. its got currupt after power failure i have back of database before 2 days but i dont have backup of one day transactions. now i tried ...
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Find repeating tickets with more than one criteria

Lets say I have 2 tables: atms & tickets each atm has many tickets. ATM table: ID | NAME ------------------------- A0109 | ATM 1 A0227 | ATM 2 etc. | etc. Ticket table: ID | ATM | ...
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Does union all have an enforced ordering

I know that a union does a de-duplication so can jumble the results, but I can't find a definitive answer for union all Example query select id from ( select id from table where id = 1 union all ...
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Amazon RDS - Can't access MySQL DB from local machine

I read many questions/answers here but they are from a different interface from AWS Console. I created a DB Instance but can't create a rule in the security groups that's allows me to connect from my ...
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How to join the tables in mysql to get wall messages and comments with name of person ? Only user and his friends messages

I have four tables in my mysql database as shown in the image url provided. I want to select data from the tables without duplication. I want to show messages and comments on wall according to the ...
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MySQL database problems all of a sudden— users' programs can't connect, I saw error 2013, error 32

I am editing my problem, based on what I've researched and done: Hi This is mysql running on an osx server. We suddenly have an issue where only one of anything can seem to connect to mysql at ...
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Mysql Replication Master/Slave and Master/Master

Looking for some insight and opinions from some DBAs, as I've been tasked to look into using Master/Master replication for a single table in a database. We currently run mysql replication using a ...
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Issue with MySql upgrade from 5.1 to 5.6 for Jboss SOA - p v 4.3

We are using JBoss SOA P v- 4.3, we have recently upgraded Mysql version to 5.6 from 5.1 and are facing some issue with the jboss start up. We are using MySQL instead of Hypersonic database for Jboss ...
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296 views

Prepared statement execution with variable number of parameters to be bound

Some stored procedures I work with need to interpolate WHERE criteria based on if procedure input parameters have been supplied. To avoid potential injection points, I'd like to utilize parameter ...
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MySQL Space efficient way of storing indexed key-value pairs associated with table

We're storing transactions in an accounting system using two tables, one contains the general description of the particular transaction (the other contains the entries, one for each account - which ...
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MySQL aggregation count performance

I have a table with about 30 million records, and I'm doing a query where I can group by field Year and count the results for that year. The table structure looks like: id | year | amount The ...
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Why does CAST(1 AS SIGNED INTEGER) return a BIGINT on MySQL?

If I do CAST(1 AS SIGNED INTEGER) I always end up getting a BIGINT returned, for example: $ mysql -u root -p --column-type-info Enter password: --- Copyright and help message snipped for brevity --- ...
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#1046: No database selected in phpMyAdmin

I have a problem with phpMyAdmin. When I click on any database on the left I get an error like: SELECT tracking_active FROM.`pma_tracking` WHERE db_name = 'information_schema' AND table_name = ...
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MySQL: index statistics dropped when table dropped?

When a table is dropped, are its index statistics also removed? The reason I ask is that I was hoping to 'prep' the stats by running log playback via the percona-playback tool prior to cutting over ...