Databse

What is the best way to reduce the size of ibdata in mysql?

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MySQL Cluster

The busiest file in the InnoDB infrastructure is /var/lib/mysql/ibdata1 This file normally houses many classes of information (when innodb_file_per_table is 0) Table Data Table Indexes MVCC (Multiversioning Concurrency Control) Data Rollbacks Segments Undo Tablespace Table Metadata Many people create multiple ibdata files hoping for better diskspace management and performance. It does not help. Unfortunately, OPTIMIZE TABLE against … Read more

Set Up MySQL Master-Master Replication

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MySQL Cluster

Here we will help you to set up Master-Master replication between MySQL servers. In this setup if any changes made on either server will update on an other one. Setup Details: Master-1: 10.0.10.12 Master-2: 10.0.10.18 Database: empmaster Step 1. Set Up MySQL Master-1 Server Edit MySQL configuration file and add the following lines under [mysqld] section. Restart … Read more

remove duplicate mysql table

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ALTER IGNORE TABLE `cdr` ADD UNIQUE(`uniqueid`)      

How to convert all tables from MyISAM into InnoDB?

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If you omit the ENGINE option, the default storage engine is used. Normally, this is MyISAM, but you can change it by using the –default-storage-engine server startup option, or by setting the default-storage-engine option in the my.cnf configuration file. You may also want to change the default storage engine just for the current session. You can do this by setting the storage_engine variable: SET storage_engine=INNODB; … Read more

innodb vs myisam : comparision of mysql database engines

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MySQL Cluster

MYISAM: MYISAM supports Table-level Locking MyISAM designed for need of speed MyISAM does not support foreign keys hence we call MySQL with MYISAM is DBMS MyISAM stores its tables, data and indexes in diskspace using separate three different files. (tablename.FRM, tablename.MYD, tablename.MYI) MYISAM not supports transaction. You cannot commit and rollback with MYISAM. Once you … Read more

mysql database replication : How To Step by Step: master -slave replication

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Here we will help you to setup master-slave replication between MySQL servers. Setup Details: Master Server: 10.0.10.12 Slave  Server: 10.0.10.18 Database: empmaster 1. Setup MySQL Master Server Create an mysql account on Master server with REPLICATION SLAVE privileges to which replication client will connect to master. Block write statement on all the tables, so not … Read more

JOINs in MySQL and Other Relational Databases

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INNER JOIN (or just JOIN) The most frequently used clause is INNER JOIN. This produces a set of records which match in both the user and course tables, i.e. all users who are enrolled on a course: SELECT user.name, course.name FROM `user` INNER JOIN `course` on user.course = course.id; LEFT JOIN What if we require … Read more