MySQL 5.5 brought many performance enhancements and expanded the feature set of the popular open-source RDBMS.

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Is there any value in adding a pk column to an composite index? [duplicate]

I recently inherited a database with indexes that contain the table's primary key as part of some composite indexes. Given MySQL adds a hidden column representing the PK regardless of whether you ...
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1answer
60 views

Migrating MyISAM tables from 5.5 => 5.6

I was wondering if anyone had any pointers on migrating MyIASM tables from mysql 5.5 to 5.6, specifically using Percona builds, via an rsync? Is this safe? I know we need to do a full ...
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2answers
47 views

How can I store least used table files to a slower drive?

Is it possible to separate the least used and most frequently used data files on to separate disks when using InnoDB?
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1answer
31 views

How to decipher the transaction message in innodb status log.

I have several transactions that seem have stalled. Looking at the innodb status log, I found several messages similar to the following: ---TRANSACTION 69DBBB, ACTIVE 947 sec starting index read, ...
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1answer
70 views

How to store temp tables in memory during table “optimize”?

When optimizing tables, SHOW PROCESSLIST lists it as "copying to tmp table". I'm trying to ensure the copy takes place in memory to speed up the process. I've tried adjusting the tmp_table_size to ...
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2answers
43 views

Mysql Master Offline

In a unidirectional Master-Slave setup, should the slave be manually stopped in cases where the Master is offline due to Maintenance, Crash etc. ? Or should one just leave it so that it keeps trying ...
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1answer
78 views

What is the difference between uniqe index/unique/unique key/unique constraint keywords?

I am using mysql 5.5.16 What is the difference between the following DDL statements? 1) create table sql_query ( id int not null , query_text varchar(21826) not null , query_md5 ...
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2answers
372 views

Fastest way to create local copy of live InnoDB MySQL database?

We have a MySQL database (InnoDB) on our live Ubuntu 12.04 server which has grown quite large (25gb+). Every month or so we need to copy this database to our development machines to work on locally. ...
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2answers
100 views

MySQL Slave not updated

This might be a duplicate of questions on the same problem asked before. But all the suggestions to the previous questions do not seem to work in my case. I have set up Replication using SSH Tunnel. ...
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1answer
470 views

Space not reclaimed after dropping MyISAM table

I just dropped a rather large MyISAM table (~4 gb); it was 350k rows with about 11k of data per row. However, when I run df -h on my database server, I am still at 100% disk usage, so much so that I ...
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1answer
88 views

How to create two same name databases in two different MySQL users?

I am using MySQL 5.5 running on Ubuntu 12.04. I have created two different users as 'root' and 'abc' and I want to create 'Items' database in this both user accounts but I want this two databases ...
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3answers
106 views

How to update cust_id from Customer table to order table Cust_id field while inserting customer name using trigger

I have two tables 1. Customer_details and 2. Order_details. 1.Customer_details table -->fields--> Cust_Id(Primary Key) and Customer_Name, 2.Order_details table --> fields-- Ord_Id(Primary ...
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205 views

#2002 Cannot log in to the MySQL server / Connection for controluser as defined in your configuration failed

I use PHP/MySQL in Ubuntu 13. To reduce the size of ibdata1, i followed this post What is the best way to reduce the size of ibdata in mysql? and make necessary changes as told in the answer. I did ...
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0answers
24 views

How to acheive Concurrency in mysql when there is 500+ request simultaneously to the server

I am using Mysql (InnoDb), in this I am facing problem when we checked the curl request upto 500 connection at a time (simultaneously) but when we try more than that then my servers goes to idle ...
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2answers
251 views

How can I execute multiple statements at once in MySQL Workbench?

I'm trying to execute multiple LOAD DATA INFILE statements at once using MySQL Workbench. However, they execute one at a time. Anyway of forcing them to run in parallel? Thanks for the help!
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2answers
96 views

Is there a rule of thumb regarding the size and number of a buffer pool instances?

I know the consensus seems to be approximately 75% of ram should be dedicated to the buffer pool. But, I'm more interested in the optimal number of buffer pool instances. What are some things to ...
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3answers
2k views

effective mysql table/index design for 35 million rows+ table, with 200+ corresponding columns (double), any combination of which may be queried

I am looking for advice on table/index design for the following situation: I have a large table (stock price history data, InnoDB, 35 million rows and growing) with a compound primary key (assetid ...
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1answer
122 views

How to overwrite csv file of MySQL result set?

My SQL query is given below, select company.Company_name as COMPANY_NAME, IFNULL(followup.contact_date, ' ') AS FOLLOW_UP_DATE, IFNULL((select Full_name from user where user_id = followup.user_id), ...
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1answer
175 views

update variable from multiple tables in one row

I have two databases, and I need to UPDATE variable 'birthday' from one row to another checking 'name' (from db1 to db2). The problem is, that 'name' variable in second db is located in another table ...
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57 views

How to update Status using IF Condition in Mysql trigger

I'm trying to write an update trigger that will Design_Update_Status to Customized when a date is entered in Custom_Design_Update_Date field and if nothing is entered that field it should update ...
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1answer
67 views

Need help on query optimization in MySQL

Below is the query, I need to optimize it. It is using subquery, I need to re-write it using join how to do this SELECT Client_ID FROM SQL_AuditPro.clients c WHERE (SELECT ...
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1answer
5k views

SUPER privilege not defined for master user in Amazon MySQL RDS

I have created one medium instance on amazon rds in asia pecific (singapore) region. i have created my master user with master password. and it is working/connecting fine with workbench installed on ...
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1answer
39 views

MySQL is not logging queries into log file

I am using MySQL 5.5 with Amazon Linux 2013. Following is my configuration for log file. slow_query_log = 1 long_query_time=0 log-error = /var/log/mysqld.log slow_query_log_file = ...
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3answers
53 views

MySQL backup breakes a table every time

I've a MySQL Server 5.1.58-1ubuntu1 installed on an Ubuntu 12.04 LTS. Every night we do a backup of all the databases with this script: rm -rf /var/backup/mysql/ * for i in $(echo 'SHOW DATABASES;' ...
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56 views

Immigrate to file-per-table mode in MySQL

I have 20 MySQL databases and in each there are about 20 tables. All the data is saved in a file called ibData1. Now I discovered about the file per table mode but if I change the value in the my.ini ...
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42 views

What's the complexity of renaming a column in MySql?

We want to rename a column in our MySql (version 5.5) database with something like this: ALTER TABLE t1 CHANGE a b INTEGER; Is this an O(N) (N=number of rows in the table) or an O(1) operation? I ...
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2answers
98 views

Show Users That Connect To DB

We are using Maria DB (v5.3 I believe) in our production environment. One issue that we have, is that historically, the dev user (which has full rights and privileges) is used in all applications ...
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2answers
35 views

Mysql used key changes between two consecutive EXPLAINs

I have a huge unmaintained innodb table (~1.5billion rows), I just started to try to query it. I write && instead of AND once; and surprise! it uses different key! EXPLAIN EXTENDED SELECT * ...
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1answer
274 views

Generate INSERT statement from SELECT query

I have two databases, in first database I have a table called zoom_city and in the second database I have a table called courrier_city. The SQL for each is below: CREATE TABLE IF NOT EXISTS ...
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1answer
675 views

how to autoincrement varchar datatype depending upon the product details name using trigger

I have a product details table, the fields in the table are *Prod_Id, Product_Name, Quantity, Slno*. Now i have created trigger for varchar data type field and implemented auto increment for Prod_Id ...
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3answers
443 views

MySQL varchar(255) limitation & Anomaly

I have defined a column in my MySQL database as : ALTER TABLE `my_table` CHANGE `desc` `desc` VARCHAR( 255 ) CHARACTER SET latin1 COLLATE latin1_swedish_ci NOT NULL However, when I enter text ...
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3answers
69 views

Contains statement Query

I need to check the string with the column if the column contains that string or not. example:String 'how to make pizza' and the column if has 'pizza' i need to fetch that.. like SELECT * FROM ...
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74 views

MySQL query with order by decreased performance

Here is my schema: CREATE TABLE `UserMst` ( `UserID` mediumint(8) unsigned NOT NULL AUTO_INCREMENT, `EMailID` varchar(50) DEFAULT NULL, `UserName` varchar(20) DEFAULT NULL, `FullName` ...
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3answers
842 views

Backup / Export data from MySQL 5.5 attachments table keeps failing!

Can anyone please help! - I have a large table in a MySQL 5.5 database. It is a table which holds a mixture of blobs/binary data and just data rows with links to file paths. It has just over a million ...
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19 views

MySQL: Archival How to?

I would like to know the correct Archival Strategy for my DB Schema. We are using Mysql 5.5. Here is the full scenario: We have around 35 tables in DB out of which 10 would be transactional in ...
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3answers
5k views

MySQL InnoDB crash post-mortem

MySQL crashed on me this morning. With the exception of the standard MySQL included databases everything I use is InnoDB. I attempted to restart the MySQL daemon but it failed twice. I then ...
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1answer
552 views

SQL Query is sometimes slow, sometimes fast

I have two hosts, one with my rails app, one with my MySQL database. Going through my rails Logfile I can see that sometimes queries take much more time than the same query at other times. Think 200ms ...
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1answer
486 views

InnoDB - How to get top locked tables and rows which are locked

I was searching for a tool OR query which can give me top locked tables and which particular row is locked, Is it possible to get ?
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1answer
31 views

Check whether MySQL Innodb Rows are compressed

After setting the various variables to enable compression on the Innodb Barracuda tables, what query will you use to check that those tables are indeed compressed?
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82 views

Performance with IN clause

Does indexed data affect query performance? means If I passed value as 1,2,3,4... in ordered form in any IN clause, can it improve query performance? and what happen in case I pass value randomly ...
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1answer
160 views

XML dump of MySQL database don't include foreign key constraints. What can be the reason? sqldump(.sql) file list it

I am accessing schema information of databases in XML format. I am taking dump of the database in XML format using the command below. mysqldump --no-data --xml -u root -p bakerydb > bakerydb.xml ...
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3answers
480 views

Getting 0KB of size file while backup mysql database using mysql dump

I am using below code to backup my database using php script but I am getting 0KB size file. How can I backup my full database with all routines and functions? $dbhost = 'localhost'; $dbuser = ...
3
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1answer
198 views

Online Schema migration in MySQL : When to start?

I'm the tech lead of a Social Media SAAS, where we're currently experiencing a big increase in data amount we're storing in our mySQL-database. We're having a single MySQL db, and besides many ...
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43 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 ...
2
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1answer
211 views

In MySQL, does the order of the columns in a WHERE clause affect query performance,why? [closed]

I have a query that doesn't use any indexes: SELECT 32, guid, 1, 1, 1, 0, 5 FROM test WHERE level >= 20 AND ( ( fun_GetIndexValue(data, 354) ...
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3answers
27k views

Why does InnoDB store all databases in one file?

It was convenient that MyISAM used to store each table in a corresponding file. InnoDB has made advancements in many aspects, but I wonder why InnoDB stores all databases in one file (ibdata1 by ...
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2answers
337 views

MySQL Synchronous Replication on Ubuntu 12.04 with DRBD

I have been looking around for some easy and open-source ways to handle database synchronous replication. DRDB on a Linux server seems to be one of the fastest and easiest methods to handle database ...
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0answers
166 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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2answers
540 views

Innodb table is taking randomly long time to execute the insert query and in show processlist showing as queryend/updating

Innodb table is taking randomly long time to execute the insert query and in show processlist showing as queryend/updating and it happens for the similar queries for the same table and the queries got ...
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2answers
319 views

Cannot stop MySQL 5.5 replication threads

We have a master-master replication setup using MySQL 5.5. On one of the servers I am trying to stop the slave thread, but without success. To ensure that the replication does not connect to a real ...