MySql

Help and howto do things in MySQL

MySQL is the world’s most popular open source database, recognized for its speed and reliability, and is frequently used with PHP to create websites. The Electric Toolbox website uses MySQL as its database backend, and I have personally been using MySQL since 1999. In that time it has proven itself to me to be an extremely fast and reliable database management system, although the earlier versions lacked some features found in other database systems, such as stored procedures, triggers, sub selects and joined table updates. Most of these are available from the 4.1 and 5.0 releases.

If you are looking for MySQL databases – for example geographical databases, I suggest you take a look at SQL Dumpster

MySQL Query Cache

MySQL has a query cache which caches the results of SELECT queries, if enabled. This means that frequently used database queries will run much faster, because the data resultset will be read from the cache instead of having to run the query again. The MySQL query cache is available from MySQL 4.0.1. Whenever tables in the database are modified the relevant entries in the query cache are flushed so you can be certain that even with the query cache enabled only up to date data is returned.

Backing up MySQL with mysqldump

A simple way to back up MySQL databases is with the mysqldump command line tool. Mysqldump can be used to back up a single database or multiple databases, and can backup MySQL databases into a text file conatining multiple SQL statements, or into CSV or tab delimited text files.

Using mysqldump to save data to CSV files

Yesterday I looked at basic use of mysqldump for backing up MySQL databases. Today I will look at how to use mysqldump to dump the data from a MySQL database into CSV and tab delimited text files, instead of using SQL insert queries which is the default dump method.

Restore data from a tab delimited file to MySQL

Yesterday I looked at using mysqldump to save data to CSV files, which by default saves the exported data as tab delimited files. Today we will look at how to restore data from these files into a MySQL database. It’s very simple to do, using the mysqlimport command line tool.

Showing running queries in MySQL

MySQL has a statement called "show processlist" to show you the running queries on your MySQL server. This can be useful to find out what’s going on if there are some big, long queries consuming a lot of CPU cycles, or if you’re getting errors like "too many connections".

Selectively dumping data with mysqldump

mysqldump is a command line tool for outputting table structures and data and can be used for backups etc. By default mysqldump will dump all data from a table, but it is possible to select which data to be exported with mysqldump. This post looks at how to do this.