MySQL : Open-Source, Relational Database Management System

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242 views

Single database won't load MySQL

When I turned off my MySQL server, and turned it back on, it wouldn't read my database anymore. Just a single database, everything else in mySQL was fine. When I try looking at any of the tables it ...
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32 views

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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2k views

MySQL - high CPU usage (MyISAM tables)

We have a server running LAMP stack on CentOS release 5.6 (Final) MySQL is having high CPU usage constantly which causes server to lag as shown top - 13:50:47 up 80 days, 13:53, 1 user, load ...
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395 views

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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67 views

Count how many locks required for a MySQL (InnoDB) query

I'm performance tuning a very data-heavy mysql application. It has a purge system that often seems to cause lock timeout errors for users. Based on my research I have a few adjustments to the query to ...
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2k views

MySQL Queries taking too long to execute

I have a database table, with 300,000 rows and 113.7 MB in size. I have my database running on Ubuntu 13.10 with 8 Cores and 8GB of RAM. As things are now, the MySQL server uses up an average of 750% ...
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101 views

Understanding Indexes and using them better

I've been spending some time trying to optimise our MySQL queries that we use which essentially joins one table with 2 million rows onto another which has 1-2 million. I know MySQL is able to easily ...
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129 views

Does it make a difference to add the DEFAULT keyword in CREATE TABLE?

The MySQL manual says: CREATE DATABASE db_name [[DEFAULT] CHARACTER SET charset_name] [[DEFAULT] COLLATE collation_name] ALTER DATABASE db_name [[DEFAULT] CHARACTER SET charset_name] ...
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1k views

Mysql slow writes

i have a strange problem with mysql. My selects goes fast. My insert/create/delete/drop/update go very slow. I have done some tests on 2 machines. My old machine and my new machine. Old is worst ...
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119 views

Why does MySQL force the tradeoff between swallowing errors and leaking commits in transactions?

Referring specifically to the choice of whether to use DECLARE EXIT HANDLER FOR SQLEXCEPTION. If you use it, you swallow errors and there doesn't seem to be any way to access them programmatically, ...
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2k views

How to prevent “ibdata files do not match the log sequence number”?

I am dealing with a very large set of databases that are all innodb. I've enountered this on mysql restart too many times for my comfort: ibdata files do not match the log sequence number But I've ...
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455 views

MySQL replication error 1146

Any idea why there is '1146 - table doesn't exists' on 'CREATE TABLE IF NOT EXISTS...' statement. It actually happened only on one of the slaves (there are two in total): Last_SQL_Error: Error 'Table ...
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739 views

The nature of the relationship between two tables in MySQL

Good day. I'm designing a database for a research project where we're predicting whether or not young female athletes will rupture their ACL(s) based on the nature of a test jump recorded with a ...
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105 views

MySQL Partitioning Performance

I have a MyISAM table with billions of rows that is still causing me problems because the indexes, even after I shortened them as much as possible, do not fit in my 64GB of RAM. I am unable to index ...
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145 views

Changing Charset to utf8 for all the fields and tables in mysql

How should I use the mysql and awk to change the charset for all the fields and tables for a specific database? I did not include username or password, so for sure it will not work. Should I run it ...
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3k views

Achieve PostgreSQL hstore functionality in MySQL

Please suggest any MySQL 5.5+ Engine that can support collection of key-value pairs be stored in any column of a table. I don't know if this feature is available out of the box in MySQL like ...
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82 views

How can one improve the performance of a query that selects on a low cardinality column in MySQL?

I have a "State" column that has a low cardinality (three possible value), on which most of my queries perform an equality selection (WHERE col = 'blah') AFAIK you need something like a bitmap index ...
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735 views

MySQL: Improve performance for one row insert into table with unique constraint

I have a table with ~ 40 mil records, with a unique index on the url collumn, of type varchar(255). Now the insert speed is about 30/s, is this expected? how could I improve it? I can't use bulk ...
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491 views

Incorrect data when we using the CONVERT_TZ function on DST boundaries

We have a problem in converting time zone from "America/New_York" to "UTC". This problem occurs only on times representing 2.00 AM during the daylight saving. Timezone conversion with correct output ...
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3k views

'Access Denied' in MySQL on AWS RDS

I'm trying to use an ETL (in my current case, the free version of Talend). I've successfully set up a MySQL on Amazon RDS, logged in through the MySQL Workbench for Mac, and uploaded my company's ...
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1k views

MySQL Server hitting 100% unexpectedly (Amazon AWS RDS)

We've been struggling with this issue for months. This week we upped our RDS instance to the highest performing instance and although the occurrences have reduced, we're still seeing our database ...
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82 views

MySQL Partioning: Is there a performance tradeoff between number of partitions and size of each partition?

I have a large table (several 100 million rows) that I would like to efficiently partition. My question is whether there is a tradeoff between partition size and number of partitions. As far as I ...
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200 views

Get all comment.message, status.message, users.* and profiles.* where users.user_id exists in friend.friend_id or friend.user_id

I need some help building this query because it's a bit complicated at least for me. I need to get all comment.message, status.message, users.* and profiles.* where users.user_id exists in ...
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1k views

MySQL re-install fails under Mountain Lion

I have problems to reinstall MySQL on Mac OS X after it was running on my system. I uninstalled it because the PreferencePane wasn't working as expected, using the procedure described here: ...
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799 views

Index usage for database server

How can i fix the Index usage on one of our database server? It says from our Nagios control panel that: Service: DB Index Usage Host: MySQL Cluster Address: ( our IP ) State: CRITICAL Additional ...
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1k views

SQL query optimization in Prestashop e-Commerce solution

I'm working on a layered navigation module within Prestashop e-Commerce solution. I'm trying to optimize a SQL query which creates a temp table during execution. I think this is creating a ...
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101 views

Can't connect to MySQL Cluster Storage (data) nodes

I've deployed a MySQL Cluster with a few nodes, and I want to access the storage nodes directly from another machine using NDBAPI. When I tried to connect from the same host it worked, but when I try ...
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319 views

MYSQL & Access ODBC

I am trying to connect mysql with access, i am settings up the ODBC correctly from the data sources, however i get a driver error. I am using access 2010 and the driver version of the ODBC conector ...
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18 views

Best database design for website ranking

I am working on a project in which I need to rank websites in two way - Global rank and their rank in a particular country. There are various factors based on which both are calculated. There are ~200 ...
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29 views

MySQL - Truncated incorrect datetime value on update statement

I have an application which produces log files. These log files include a Timestamp field in the format 2015-08-25T09:35:01 UTC. (there will be apx 60 logs produced at 0.25 GB per day). I need to ...
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43 views

Is not having 'named' timezone support common in MySQL?

I'm trying to set the timezone the database uses using: "SET time_zone = 'UTC'; Whilst this works on my development server it doesn't work on my staging server; I get this error: General error: ...
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23 views

Organizing databases and tables in phpMyAdmin

I have 2 servers, on one server the access6_identical sql file is on the second directory under identical as can be seen here: On the other server, it is on the parent directory as can be seen ...
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10 views

MySQL/Percona Audit Log Plugin Not Working

I've been looking to implemement the Percona Audit Log plugin. So far I have installed it and configured it, and it seems to be working ok. Except, I have installed it on a slave Database as I don't ...
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55 views

Space usage when copying

Short version Copy table took up more space than I expected or tested Why would that be? Could it be the replication / binlog? If so, what then is written to the binlog during this query: INSERT ...
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20 views

Update remote MySQL database upon changes in local SQL Server database

I have a Web store running with MySQL on the remote host. And I have inventory management software using Microsoft SQL Server on my local system. I want to update product stock in the web store when ...
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48 views

MySQL server slow due to too many information_schema queries

Recently our server has been slow due to too many slow information_schema queries, which I am unable to kill. Please see the screenshot below: These queries are taking over an hour to run each. ...
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33 views

Replicate existing database live

New to db admin here and I have a question. My setup is Windows Server 2012 R2, MySQL, using MySQL Workbench. I have Database A on Server A, how can I make an exact clone of this database (Database ...
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37 views

insertion creates duplicate with same data

I am using MySQL with PHP. I fetch data from a third party using SOAP. I have an issue with duplicate insertion of data. This occurs once or twice a day. Say there are 10 records ready to enter into ...
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60 views

MySQL Master-Master Crash-Safe Replication: Slow UPDATE times

Environment 2 MySQL version 5.6.26 Dedicated MySQL Servers connected on a LAN. Servers Have 16 Cores with 32 GB RAM each and are really fast. Master-Master Crash Safe Replication is setup on both ...
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26 views

MySQL Server Instance Configuration Wizard does not start for the first time

I tried to install MySQL on my machine (win 8 64 bit). I downloaded mysql-5.6.24-winx64.exe and after completing the MySQL 5.6 setup wizard, MySQL Server Instance Configuration Wizard does not start ...
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27 views

mysqld stops right after starting because of corrupted tables (disk full + hardware reboot) - how to fix it?

I'm dumb, I did the stupidest thing I could. On one of my servers, the SSD was full and I wasn't aware of it. The high-traffic website became working really slow, then started displaying errors, ...
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30 views

Update row value with a sub-select join

I am trying to update 1 column in all rows in a table to have an appropriate count value. Sadly, the SELECT query I am using won't let me join on a field in update table. The query looks like this ...
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96 views

Slow Tally Tables

I have a pain point with a relatively large application concerning 'tally tables', which are used for keeping track of the number of items against 'campaigns' (placed by a client), and 'publishers' / ...
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47 views

Tuning MySQL MyISAM for large joined updates

I have a database with two tables that I would consider small. I need to update values on the larger of the two tables (1,100,000 rows, 75M MYD, 120M MYI) from the join of the two tables. The smaller ...
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23 views

Caching impression counts to avoid mysql inserts

We currently get a LOT of mySQL inserts/updates on duplicate daily (millions) and we're looking at speeding up the application by using some form of counter with memcached and then clearing it on ...
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56 views

Get average of multiple rows with criteria and return those rows

I'm attempting to get any items that are the same type, but are ranked one higher that have an average equal or greater than the item ranked below. I have a table and query like ...
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24 views

How do you output field changes in mysql the most efficiently?

I have a rather large employee feed coming in and each employee has about 50 fields. I take the employee data and add on a bunch of other stuff and this gets outputted to one of our vendors. Most ...
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26 views

Select records where difference between datetime column1 and column 2 is greater than X amount of time

As the title indicates, I'm trying to return records where the datetime difference between two datetime columns is greater than X amount of time. I'm having trouble wrapping my head around this ...
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39 views

Single Redshift table vs several mysql/ pgsql (on RDS) tables for small (200 tables * 20 columns * 1 million) monthly aggregation data

We're providing SaaS Data Analytics Dashboard for around 200 clients. We're using Amazon Redshift for storing data in in around 5 tables. We're getting around 30 million hits per day. Currently our ...
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33 views

I need to find the “rank” in a sub-set of entries

I am currently working on some sort of a highscore list. But values displayed are individual for each user, ie. limited by constraints. One constraint that I am currently working on is "being part of ...