MySQL

The InnoDB storage engine uses a hashing algorithm to find the dictionary, and its conflict mechanism takes the form of a linked list, and the hash function uses the division hashing method. For a buffer pool page hash table, a page page in the

1, if there is an or in the query condition, even if the condition of the query with an index will be invalidated, if you want to use or, and do not want to invalidate the index, you can only add all the columns in the OR condition index2, like

There are many ways to convert a table's storage engine to another engine, each with its pros and cons:A:alter tableThe simplest way to change a table directly from one engine to another engineALTER TABLE Tb_name ENGINE=INNODB;Note: This method

The simplest way to page pagination is this.Select * from ORDER by desc 10000,tenThe table has around 5w of dataThe average execution time is around 10s, so the query is very inefficient in the case of large data volumes.There are several ways to

It takes a lot of work to introduce memcached into the application. MySQL has a handy query cache that can automatically cache the results of SQL queries, and cached SQL queries can be executed quickly and repeatedly. How does memcached compare with

var mysql = require (' mysql '); var pool = Mysql.createpool ({host: ' localhost ', User: ' Root ', Password:root, DA Tabase:demo, port:3306}), function Mysqlhelper () {};function querysql (Querysql, callback) {Pool.getconnection (func tion

1. Under the server, create the following 3 folders: Mkdir/bak,mkdir/bak/bakmysql,mkdir/bak/bakmysqlold. Build a shell script under the/bak/bakmysql folder: touch/bak/bakmysql/backup.sh. Authorization to File: chmod 755/bak/bakmysql/backup.sh.2.

TodaySELECT * from table name where to_days (Time field name) = To_days (now ()); YesterdaySELECT * from table name WHERE to_days (now ()) –to_days (Time field name) 7 daysSELECT * from table name where Date_sub (Curdate (), INTERVAL 7 Day) date

1) Use of B + Tree index in different applicationsFor OLTP applications, since data volume acquisition may be a small fraction of the time, building a B + Tree index is an objectionFor OLAP applications, the situation is complicated because the

1. Theoretical knowledge1.1. Introduction of PamPluggable authentication Modules, Pam, is a miniature pluggable authentication module (PAM is a acronym for pluggable authentication Modules)1.2, Pam's workflow650) this.width=650; "src="

" problems introduced after data splitting "The problem of data horizontal splitting is mainly only through sharding key to read and write operations, such as the Sharding key to the userid of the segmentation example, read the details of the UserID,

By default, fields in the MySQL database (char, varchar) are retrieved (where) or sorted (order) in case-insensitive.In many application programming, there is a case-sensitive requirement, which can be achieved by defining the binary attribute

1.mysql failed to initialize:Mysqld-initialize is a failure because it was previously installed, removed later, and is now reinstalled.Workaround:1) command line execution: mysqld--initialize--user=mysql--console2) Execute the above command first to

1. Change the table method.Please use MySQL management tools such as: SQLyog EnterpriseIt may be that your account is not allowed to log on remotely, only on localhost. This time, as long as the computer in localhost using the MySQL management tool

There was a time when a log was set to query SQL statements in MySQL that are slower than 1 seconds. Just suddenly recalled the method of setting, there are several parameters of the name of the dead and alive, so re-organize, make a note.The

The relational database relies on the primary key, which is the cornerstone of the database physical pattern. There are only two uses of the primary key at the physical level:Uniquely identifies a row.As an object that can be effectively referenced

Data preparationCreate a database, import data[Email protected] ~]# mysql-uroot-p-E "CREATE database viewdb;"Enter Password:[Email protected] ~]# mysql-uroot-p viewdbEnter Password:mysql> show databases;+--------------------+| Database |+------------

① using a composite index (UserName, userage) ② using a composite index (USERAGE,USERNAME)1.select * from T_user where userName in (' DD ', ' GG ') will use the index under ② without indexing under ①;2.select * from T_user where userage=3 will not

MySQL deadlock caused by load data statement, mysqlload The deadlock reported by an online project briefly describes the causes, solutions, and related points. 1. Background This is a project similar to DATA analysis. DATA is completely imported

Import of large MySQL Data Volume and MySQL Data Volume First: in fact, the best way is to directly use: Mysqldump-u username-p Password Database Name In linux, we tested a data import of over 10 thousand rows, totaling 121 MB. In linux, the