MySQL

After you delete a large amount of data in your library, you may find that the data file size does not decrease. This is caused by the fragmentation of the data file after the delete operation. discuz! In the system Number setting interface provides

The database engine you can use depends on how MySQL was compiled at the time of installation. To add a new engine, you must recompile MySQL. By default, MySQL supports three engines:ISAM, MyISAM and heap 。 the other two types of InnoDB and Berkley (

A friend emergency: MySQL forgot the root password let me help to see, because no contact with MySQL so from the Internet to find information By my own practice has been successful! The MySQL version is 5.1. The following is a modified information

Today to a customer inspection of the situation issued from the library does not have the business situation MYSQLD CPU's a core occupies 100%. Chacku Slow query also does not have written SQL.It can be said that the simple process of copying a CPU

Today, I'm going to help my colleagues with a SQL (Simplified) execution error: Mysql> Select Date_format (' 2013-11-19 ', ' y-m-d ') > Timediff (' 2013-11-19 ', ' 2013-11-20 '); ERROR 1267 (HY000): illegal mix of

During the execution of transactional statements, the server will perform additional processing, and multiple transactions are executed in parallel while the server is executing, in order to bring their records together, the concept of transaction

1. New database: After entering the phpMyAdmin management interface, find the following text, "Create a new database," and then fill in the name of the database you want to create, and then select the encoding of the database in the following

The basic idea is: In JS dynamically create Select control option, through Ajax to obtain in PHP from the SQL database to obtain the city and province information, the code is a bit long, but many are similar, such as JS in the province, the city,

Through the status command, view slow queries this item, if the value is long >0, the query execution time is too long Copy Code code as follows: The following are the referenced contents:mysql> status; -------------- MySQL

Problem description One user reflects the first line one SQL statement execution time is too slow to accept. The SQL statement looks simple (the table name and field name are modified in the description):SELECT Count (*) from a JOIN b in a. ' s ' =

To know the size of each database, the steps are as follows:1, access to the INFORMATION_SCHEMA database (the information stored in other databases)Use INFORMATION_SCHEMA;2, query the size of all data:Select Concat (Round (sum (data_length/1024/1024)

1. Insert data to derive from other tables Table A has ID, cola fieldTable B has ID, cola, colb ... Fields, where the IDs are all primary keys, cola as columns of the same nameNow you want to insert the colb>1000 records from Table B in Table A,

This article describes the MySQL query time period method. Share to everyone for your reference. The specific methods are as follows: MySQL query time period of the method is not everyone will, the following for you to introduce two MySQL query

1, Sharding application scenarios are generally those? When the amount of data in the database becomes larger and bigger, the pressure becomes larger, both read and write. Imagine, if the data in a table reached tens of millions of millions of

MyISAM InnoDB the difference in composition: Each myisam is stored on disk as three files. The first file begins with the name of the table, and the extension indicates the file type.. frm file storage table definition.The data

Suppose you have a table: Copy Code code as follows: CREATE TABLE users (id int (6) Not NULL auto_increment,primary KEY (ID), user_name VARCHAR (m) not null,emails VARCHAR (x) T NULL); Initialize the table and add some

MySQL contains support for triggers. A trigger is a database object that is associated with a table operation and is invoked when a specified event occurs on the table on which the trigger on which the action event touches the table executes.

The company's MySQL architecture has recently been upgraded, from the original one of the main more from the Drbd+heartbeat double master from, just have a new E-commerce site project will be online, with the Drbd+heartbeat dual-master one from,

A simple expression.MyISAM is a non transactional storage engine.InnoDB is a storage engine that supports transactions.InnoDB engines are more suitable for inserting and updating operations than more applicationsand MyISAM is suitable for frequent

Copy Code code as follows: CREATE TABLE A like B This way, when you copy table B to a, the complete field structure and index of table B are copied into table A. Copy Code code as follows: CREATE TABLE A as SELECT x,x,x,xx