Posts tagged mysql

10 posts in total.

Where is MySQL / MariaDB storage location by default on CentOS 7?

By Eric Z Ma, | In QA

Where is MySQL / MariaDB storage location by default on CentOS 7? No special configuration to the MariaDB from official repository of CentOS. On CentOS 7 Linux it is usually by default /var/lib/mysql But here I give you another “hacky” way to find it out. The method is to find out the mysql daemon mysqld’ […]

How to write a SQL to replace strings in a column in a MySQL database table?

By Eric Z Ma, | In QA

How to replace strings in a column in a MySQL database table? For example, I would like to replace http://www.systutorials.com with https://www.systutorials.com in a content column of a table post. You may use a SQL statement as follows. update post set content = replace(content, ‘http://www.systutorials.com’, ‘https://www.systutorials.com’) where content like ‘%http://www.systutorials.com%’ Answered by Eric Z Ma.

HTML form generation from the database and store value into the database

By Q A, | In QA

I have a “t_form” table and a “t_attribute” table. It looks a little bit like below. Form table form_id | form_name | description ———————————– 1 | Laptop | Possible attributes are Model, Screen Size, OS, Cd Player 2 | Mobile | Possible attributes are Model, OS 3 | Tablet | Possible attributes are Model, Screen […]

How to find out and change the storage engine of tables in MySQL

By Q A, | In QA

How to find out and change the storage engine of tables in MySQL databases? Find out the storage engine of a table in a database: SELECT ENGINE FROM information_schema.TABLES WHERE TABLE_SCHEMA = ‘database’ AND TABLE_NAME = ‘table’ Change the storage engine of a table: ALTER TABLE table ENGINE = type type can be innodb or […]

How to change strings in MySQL tables

By Q A, | In QA

How to change strings in MySQL tables? e.g. I want to change domain.com to www.domain.com. Use the REPLACE functions of MySQL: http://dev.mysql.com/doc/refman/5.0/en/string-functions.html#function_replace One example is like this: UPDATE table SET field = REPLACE(field, ‘domain.com’, ‘www.domain.com’) WHERE field LIKE ‘%domain.com%’ The WHERE clause is not needed but can make execution faster. Answered by anonymous.

MySQL at Facebook

By Q A, | In QA

Facebook uses lots MySQL databases. Any information about how Facebook scales MySQL? Some information on the Web: MySQL at Facebook’s page https://www.facebook.com/MySQLatFacebook?filter=1 A post by Ryan Thiessen, Database Operations at Facebook on Quora: http://www.quora.com/Facebook-Engineering/How-does-Facebook-structure-MySQL-so-that-it-is-robust-and-scalable And more: http://mashable.com/2011/12/15/facebook-timeline-mysql/ http://gigaom.com/2011/12/06/facebook-shares-some-secrets-on-making-mysql-scale/ http://www.wired.com/wiredenterprise/2011/12/facebook-timeline-anatomy “A lot of people are surprised that for this shiny new thing for Facebook, we’re using […]

How to repair a MySQL table?

By Q A, | In QA

After a server crash and restarting, MyBB reports a SQL Error as follows: MyBB SQL Error MyBB has experienced an internal SQL error and cannot continue. SQL Error: 145 – Table ‘./mybb/mybb_sessions’ is marked as crashed and should be repaired Query: SELECT * FROM mybb_sessions WHERE sid=’40021925bd0494ea31…’ AND ip=’x.x.x.x’ LIMIT 1 The dababase is MySQL. […]