Basics of MySQL under Linux (i)

the basics of MySQL

1. Use of help in MySQL server

Format:     mysql> help commandeg:    mysql> help  create database    Name:  ' Create database '      description:    syntax:        create { database | schema} [if not exists] db_name         [create_specification] ...    create_specification:         [default] character set [=] charset_name | [ Default] collate [=] collation_name    create database creates  a database with the given name. to use this statement,  you need the CREATE privilege for the database. CREATE  schema is a synonym for  create database.    url: http://dev.mysql.com/doc/refman/5.1/en/ create-database.html123456789101112131415123456789101112131415

2. Set a password for the user

First: Updating the user table update user set Password=password ("PASSWD") where user= "user" the second type: set password for [email protected] =pa ssWOrd ("password") Third: Use Mysqladmin command mysqladmin-u username-h host password "New password" 123456123456

3. mysql Mode of communication

Local communication: Communication based on localhost,127.0.0.1 or Lo addresses, all via Unix.socket remote communication: Communication via TCP socket 1212

4. Shortcut keys used in MySQL

Ctrl+w Delete the word before the cursor ctrl+u Delete all contents of the command line before the cursor ctrl+y paste use ctrl+w and ctrl+u deleted content CTRL + a move cursor at the beginning of the line ctrl+e move the cursor in line 1234512345

5. mysql variables

Static variables: Written in the configuration file, with the start of MySQL dynamic variable: You can modify the global variables at the time of MySQL Runtime: The current session changes the value of the variable, for subsequent connections in the session is valid query MySQL variable: mysql> show global|  session variables; Change MySQL variable mysql> show global|session variables= ""; view MySQL default character set: Mysql> show global variables Like '%char% '; change MySQL default character set: Mysql> show Global character_set= "gb2321"; 123456789101112123456789101112

6.mysql Query Statements

select query statement execution Order      start->from sentence->where statement->group by statement- >having sentence-->order by sentence-->select sentence-->limit sentence--The structure of the result SELECT statement:     select  [ALL | DISTINCT | DISTINCTROW ] [SQL_CACHE | SQL_NO_CACHE]  SELECT_EXPR [, SELECT_EXPR&NBSP, ...]  FROM TABLE_REFERENCES    DISTINCT: Specifies that the same result set is displayed only once     sql_ Cache: Cached in query cache     sql_no_cache: Do not cache query structure connection query:     left connection:     select * from a left join b     Right Connection:     select * from a right join b     Internal Connection:     select * from a join b12345678910111213141234567891011121314 

MySQL Simple architecture
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Query execution process: A.mysql after receiving a query request, now query the cache to find, if the search succeeds, execute F, if the lookup fails, execute b b. Send to the interpreter, interpret the SQL statement, then C c. Next, the SQL statement is optimized, then D. optimized sq The L statement is given to the storage engine for execution, followed by E-E. The results are cached in the query cache, followed by F. Results returned to the user

Basics of MySQL under Linux (i)