MySQL

Mysql> show Processlist;Mysql> Show status;Mysql> show status like '% under variable% ';Aborted_clients the number of connections that have been discarded because the client did not properly close the connection already dead. Aborted_connects the

Start: net start mySql;Enter: Mysql-u root-p/mysql-h localhost-u root-p databaseName;List databases: show databases;Select database: Use DatabaseName;List table: Show tables;Show table Column properties: Show columns from TableName;Build database:

1.how the MySQL partition handles null values in a partitioned field1.range partition NULL is treated as a minimum value2.list partition null value must be enumerated or an error will occur3.hash/key partition null value treated as

PS: A real-world stored procedure caseCREATEDefiner=' Root ' @ ' localhost 'PROCEDURE' Sp_delete_article_by_id ' (inch' ID 'int)BEGIN#Routine body goes here ...DECLARE Temp INT;SET @aid =ID;SELECT COUNT(*) fromGk_reply_articleWHEREa_id= @aid into

1generally, by default, Sql_mode is empty, which is not a strict SQL check.2if the Sql_mode is empty, test:Create TableTT3 (nameChar(2));//define a tt3 table with a name field length of 2Insert intoTt3Values('wo');//normal insertion, flawlessInsert

Installation of 64-bit Apache server under WindowsThe first thing to note is that the APACEH server does not have the official 64-bit version, only the folk master himself produced. The following are the specific installation steps. on the

1. MyISAM with memory support table level lock BDB page level lock 2. Table lock (not cousin) lock table read // read-only table lock, This means that after the lock is executed, the operation in the lock can only be read for the

These two days in the website move, this site moved using the form of direct packaging MySQL database and Web files to migrate, upload good MySQL data directory inside the database to MySQL storage database on the VPS, unzip on the line. The path to

/** Create a new user * * Log in to the root user using the command line tool or IDE. (Command: Mysql-u root-p)*/--Execute SQL statement insert user, want to use password method unified encryption, otherwise can't use. INSERT

It is always known that MySQL paging is written like this:select * From ' yourtable ' limit start,rowsNow, I have a table with 9969W data in my database, and it's called Tweet_data.Select COUNT (*) from Tweet_data Execute the first SQL statement,

1. myisam,bdb,innodb,memory single table supports at least 16 indexes2.Create IndexId_index onEMP (ID) Create an index of an ID field named Id_index for the EMP table3.Drop IndexId_index onEMP Delete id_index index of EMP table4. Explain xxxxxxx,

PS: This time the amount of information is a bit large.Aggregating different valuesSELECT AVG (DISTINCT prod_price) as Avg_priceFrom ProductsWHERE vend_id = 1003# The same value is not calculatedCombining aggregate functionsSELECT COUNT (*) as

Step1:Collect information, communicate with people who talk about the system, and fully understand the tasks that the database needs to complete.Example: Blog systemBasic functions: Publish and edit articles, multi-user support, full text search,

What is an index?An object in the database.The query that is used in the database to speed up the table.The disk's I/O is reduced by locating the data by using the fast path access method.Separate from the table, but cannot exist independently, and

Table's storage Engine type:MyISAM: It is mainly used for reading and writing operations, seldom updating, deleting, and not demanding the completeness and concurrency of things.InnoDB: Apply to the integrity of the things required high, in the

History of DatabaseThe embryonic stage-file systemPrimary stage-First generation database: Mesh model, hierarchical model database.Intermediate stage-second generation database: relational database and structured query statement.Advanced stage-third

12. mysql SQL _mode and SQL _mode 1. in general, SQL _mode is empty by default, that is, the SQL check is not strict. 2. if SQL _mode is null, test: create table tt3 (name char (2 )); // define a tt3 table with the name field length of 2 to insert

10. mysql transaction Introduction 1. myisam and memory support table-level locking BDB page-level locking Innodb row-level locking 2. table lock (not a table) lock table read // read-only table lock, that is, after the lock is executed, the

13. mysql partition RANGE & LIST, mysqlrange 1. range partition creation instance: create table emp (id int not null primary key auto_increment, name char (25) not null default '') partition by range (id) (define the field id as the PARTITION field

14. mysql partition HASH & KEY, mysqlhash 1. hash partition ps: I personally think the HASH PARTITION is very good and powerful, and the simple distribution is extremely even to CREATE an instance: CREATE TABLE HASH_EMP (tid int, tname char (255)