MySQL : Open-Source, Relational Database Management System

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EXPLAIN (with subqueries) is giving results I don't understand

I have a query that relies on a subquery, and that subquery relies on another subquery. When I run an EXPLAIN on the full query, in does a full table scan of the table in the primary select. However, ...
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240 views

MySQL Cluster lock wait timeout exceeded when trying to deal with huge amount of queries

I'm trying to deal with many connections and sometime I get following error: ERROR : Lock wait timeout exceeded; try restarting transaction The bigger number of queries the least number of ...
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1k views

Connect to a Remote MySQL

I'm trying to connect to a MySQL remote Server but I always get: RROR 2003 (HY000): Can't connect to MySQL server on 'IP' (111 "Connection refused") I follow this rule in the remote server GRANT ...
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271 views

Insert results of concat

I have a table with 4 columns: ID ORDER_ID QTY VALUE 1 153 1 0 2 476 1 0 3 453 9 1 4 719 2 2 ...
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87 views

MySQL: What are the pros and cons of running with engine=Memory vs on a memory-mapped filesystem?

What is the difference (in terms of read and write perf, alter tables, backup and recoverability and consistency) of running a MySQL database on a memory-mapped filesystem vs with ENGINE=MEMORY
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583 views

Nesting multiple INNER JOIN within LEFT OUTER JOIN in sql on deifferent side of keyword

I am having some problems with one of the question's answered in the book "SQL FOR MERE MORTALS". Here is the problem statement Problem Statement Here is the Database Structure The Database ...
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121 views

Combine two mySQL sum queries into one which use different where clauses

I have two sum quires referencing different tables in mySQL. How can I combine the two in order to calculate the difference between the two values for each user in the database? Query 1: SELECT ...
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99 views

How to change the domain name or IP address in mysql database in every tables

I was using Openfire chat server in Ubuntu, whose IP address was 192.168.1.15. Then, I wanted to move it to other ip (192.168.1.55), so i took a backup of my database. The database I was using is ...
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517 views

Moving datadir OK start, but socket error for mysql client

I'm trying to move my MySQL datadir from /var/lib/mysql over to /home/mysql (an ssd drive as I'm having iowait issues on /var/lib/mysql when MySQL is running on that drive). The OS is CentOS 5.6 ...
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37 views

Logging all user actions

I'm creating a community-driven project and, of course, I want to be protected against spam or evil users. In case of undesirable changes in the DB I would log all users' actions ...
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161 views

Result of query not showing in phpmyadmin

I have a 500,000 row database that I am running a reasonably complex query on: SELECT yfog, (SELECT AVG(yds) FROM pbp_yards_gained p2 WHERE p2.yfog=p1.yfog AND type = ...
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209 views

Pasting into PHPMyAdmin

This is probably really simple but I have had a look on the web but can't seem to find an answer. I am experimenting with MySQL + PHPMyAdmin on a WAMPserver stack and was saving queries in Excel When ...
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22 views

What is safe way to restore mysql database?

When database is online. I want to restore dump file to it. Here is my plan: set global read_only=ON use root with super_priv to drop all databases do restore all databases set global read_only=OFF ...
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151 views

mysqld: page allocation failure. order:3, mode:0x20

I've been running a mysql server in production for some time, lately the db has been locking up at around 10:30 every day. There's no cron jobs running at that time or anything like that, and I'm at a ...
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84 views

MySQL replication: Understanding content of binlog

I am using MySQL replication with GTID. I did mysqlbinlog to see some binary log. This is a section in binary log that I am considering: SET @@SESSION.GTID_NEXT= 'servre-uuid:248283'/*!*/; SET ...
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36 views

MySQL upgrade steps - review

I read the MySQL upgrade documentation and the upgrade questions in stack exchange and have a fairly good understanding at this point. I am an accidental MySQL dba and this is my first upgrade and ...
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36 views

MYSQL Stored Procedure Problem. Need Help

MySQL Stored procedure: Delimiter $$ DROP PROCEDURE IF EXISTS spGetCompanyNames $$ Create procedure spGetCompanyNames (IN Employer nvarchar(75), Out Employer_Namee nVarchar(75)) begin Select ...
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118 views

MySQL select query runs forever in Toad

I'm trying to run a simple SELECT query in Toad (for MySQL 7.2.0.2922). SELECT * FROM sometable When I click execute (or press F9) a small timer shows up in the status bar (bottom right) and it ...
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39 views

Conditional value lists in MySQL

apologies in advance if the language I use here is insufficiently specific. Please let me know if there's anything that I can clarify. Does MySQL provide a means of creating conditional value lists a ...
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60 views

Text comparison select query needed that finds most whole word matches within larger string

I have a database of products, many with similar names. For example... iPhone 5s (GSM model) A1533 iPhone 5s (GSM model China) A1518 iPhone 5s (GSM model China) A1530 iPhone 5c (GSM model) ...
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50 views

Markup Languages and SQL Queries

I need to store some metadata in an MySQL database. This data will need to be stored in some form of markup language and reside in a 'meta_data' field on a table. I will need to run searches ...
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131 views

Show single value of one column for multiple rows of other columns

I have a SQL query which displays my data results like this. date emp_id emp_name spent_hours 19-08-2013 1024 jack 10 19-08-2013 1024 jack 11 19-08-2013 1024 jack ...
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98 views

Auto increment holes in primary key - any issues?

I have an application that is creating large holes in the auto incremented primary surrogate key to the table as it uses lots of INSERT ... ON DUPLICATE KEY UPDATE queries. I'm looking into changing ...
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62 views

How do triggers work on partitioned tables?

I have partitioned a table on the basis of a column. This column can either have 0 or 1. So, only two partitions (p0, p1) have been created internally. On this table there are 3 triggers which execute ...
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175 views

Copying a table with its structure, indexes, and associated triggers?

I have studied this post on Stack Overflow: Fastest way to copy a table in MySQL. But no answer is copying everything like the table's structure, data, indexes as well as associated triggers. Is it ...
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27 views

Database for large dynamic network graph - best practise?

I am constructing a MySql database which is to contain data for a large network graph. There will be thousands of nodes and ten thousands of edges. The nodes and edges will be assigned a category. ...
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95 views

self join of single table to find time difference of adjacent rows of a single column which are not in sequence

I want to find the time difference between two adjacent rows of a single table which are not in sequence.i made a self join of table and tried but i did not achieve what i need .can anyone please help ...
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59 views

Load data from file only for specific column based on other column value

I am familiar with basic usage of 'load data local infile' and importing specific columns only. What I want is however to import a single column from file based/related on data from another column. So ...
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72 views

hot/live sql backup

please excuse my ignorant question as I am still fairly new to database things so I have a mysql database and a part of it has file with average size of 10M I store them in their own directory and ...
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16 views

database result encoding changed

In my web site the content from the database is suddenly appearing in the wrong encoding! When I restart mysql the encoding is fixed, but after while it is again changed to the wrong encoding and I ...
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131 views

Finding the right MariaDB configuration

I’ve read several articles about how to configure MySQL/MariaDB, but now I’m kind of confused how to find the right values. Some articles suggest not choosing to high values, others recommend adapting ...
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84 views

Mysql query with LIMIT much slower under RDS (5.6) than old 5.1 system

We inherited an old legacy system running on mysql 5.1, and moved it to RDS running 5.6. One query is running much slower - it can take up to 20 minutes to run, where previously it took only a few ...
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40 views

Restore data from MYSQL Bin log

I am trying to restore some data from mysql bin log file. But when it encounter some special characters, query gets break and I am not able to continue after that. Is there any way to handle special ...
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49 views

Show weeks based on the date range

I have a table that has Start Date and End Date. I am very new to MySQL, I was wondering what MySQL query can I use to get all the data from Monday to Friday and show in which week it falls. like ...
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73 views

Percona MySQL LDAP authentication fails through .NETmysql connector

Basically MySQL uses its native authentication, where the username and passwords are stored in mysql.user table. MySQL authenticates user against the credentials stored in mysql.user table. Our ...
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94 views

MySQL: Select a subset/range of a result

Assuming there's an application for running events (marathons etc.). An event (i.e. a run) has an ID and serveral segments, divided by checkpoints. So here's what we might get: SELECT * FROM segments ...
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10 views

tables federated in mysql say in use

I have a mysql server with 30 databases which there federated tables. At one point in the column appears collate me "in use" and I can not use those tables. I appreciate any help.
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69 views

How to manage MySQL database with Oracle Fusion Middleware?

Is it possible to connect and manage a MySQL database with Oracle Fusion Middleware?
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10 views

MySQL: Is it possible to run a search on a specific database for a specific string?

I need to find a specific email address in a database. I don't know in which table the email is set so I'd like to run a search on the whole database. Is that possible? Thanks
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411 views

Why Percona MySQL is crashing again and again

We have Percona MySQL Cluster running with three nodes on CentOS. Server : Percona-XtraDB-Cluster-server-56-5.6.19-25.6.824.el6.x86_64 One node is crashing repeatedly. Thread pointer: 0x18910ba30 ...
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46 views

Difference in dates between last 2 rows group by user

I have a orders table where each it has a column ord_user_fk which is the user and a ord_date which is the order date. One user can have many orders. I am trying to find the difference between the ...
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40 views

MySQL Event that process large data volume randomly errors

I have a MySQL event that uses a cursor to loop through a large volume of user data. Randomly, and this has only recently started happening, I am getting:- 1 queries executed, 0 success, 1 errors, 0 ...
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52 views

DataController plugin for Windows?

The MySQL DataController plugins looks to be very interesting. But how can I compile/download for Windows? The wiki page syays, available under Windows too.
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246 views

Updating +150,000 rows using .sql file causes ERROR 2013 Lost connection to MySQL server during query

I am using ubuntu 12.04. I have a .sql file that is around 5 megabytes. When I use the command: mysql -u -p -v database query.sql The server prints out the content of the file (because of --verbose) ...
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65 views

Index on fields with a function

I have a log table. It logs visitor data (time of visit, browser, window size ...). I want to create reports. I use a query like this (MySQL): SELECT COUNT(*) as raw_views ... FROM logs WHERE ...
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49 views

How to optimize having bit_or?

Let's start with SQLFiddle http://www.sqlfiddle.com/#!2/64fc5/1 I have some urls and I am making some tasks (crons) related to them. Task can be successful or not. I want to try to do it only three ...
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46 views

Problems with foreign keys in a mysql database

I am trying to link both these tables with a foreign key. But I keep getting error message "ERROR 1452: Cannot add or update a child row: a foreign key constraint fails " the foreign key is pwalk_id ...
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25 views

MySQL Optimisation

I am running mySQL 5.6.16 on a server running Centos with 20Gb RAM ad 1TB disc space. when running SELECT scripts wiht order and group by statements and a number of joins, the results can be very slow ...
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70 views

How to make changes to MySQL database settings

I'm a real DBA newbie and have learnt everything in the last day, so need basic guidance on how to implement the recommendations from MySQLTuner (which i eventually managed to do!) >> ...
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21 views

wp db issue, need help selecting table values

Hey I am trying to figure out how to select only those items that have same ID but different values in another column. it's Wordpress database structure. My table sample would look something like ...