MySQL

1. Integral typetinyint (m) One byte -128~127smallint (m) 2 bytes -32768~32767Mediumint (M) 3 bytes -8388608~8388607Int (n) 4 bytesBigInt (N) 8 bytesIf unsigned is added, the range value is doubled. such as tinyint unsigned the value range is (0~256)

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************************************************************************* * * * Original:blog.csdn.net/clark_xu Xu Changliang's Column************************************************************************Installing CMakewget

Original code:ImportOS, sys, stringImportMysqldbmysql_host='localhost'Mysql_port='3306'Mysql_user='Root'Mysql_pass="'mysql_db='app_hwms'defMain ():Try: Conn= MySQLdb.connect (Host=mysql_host,user=mysql_user,

1. Storage Engine ConceptsLet's say: A movie has mp4,wmv,avi,flv ... and other formats. The same movie has different storage formats on the hard disk, and the amount of space and clarity varies.So how does the data in our table be stored on the hard

1. Security equals operator ()SELECT NULL NULLUNION ALLSELECT NULL 1union ALLSELECT 10UNION allSELECT NULL = NULLNote the difference between this operator and equals (=) is that when you determine that two values are empty, the execution results

Log in to the database system:Mysql–h Localhost–u root–pwhere the "-H" parameter refers to the host name of the connection, so here is the connection to the machine, so the following content is localhost;The "-u" parameter indicates the user name,

1. What is a view?A view is a virtual table formed by the results of a query.2. When should I use the view?If a query result occurs very frequently, that is, you should always take this query result to make subqueries3. Creation syntax for

Write about the use of Union today and something to be aware of.Union: The union means to merge two or more query results together.Requirements: Two queries must have the same number of columnsRecommendation: The type of column can be different, but

Tutorial list: http://www.dxzy163.com/view/index7627.html 41 Stored Procedures 40 Full-text indexing and stop words 39 Index of the Tube 38 Index Concepts 37 Database backup and Recovery 36 Transaction syntax 35

Left JOIN connection:Select column 1, column 2, column n fromTableA left join TableB On tableA. Column = TableB. Column (Normal is a foreign key column) [Here the table is connected to a large table, completely as a plain watch]Where,having,group by

First, what is the index?For example, if we want to find a word in the dictionary, how can we find it quickly? That is through the dictionary directory.For a database, the function of an index is to add a directory to the ' data '.Second, the index

Read a blog, feel the work is worth learning, the original text as follows:Accident descriptionIn a project, on-line a new function, a continuous customer service to our response, there are users of individual props up to 4.2 billion, but there has

About Char,varchar and text usually do not care too much, in general, probably now everyone is using varchar. But when the content to be stored is larger, what is the choice between varchar or text? I don't know......Then went to look up some

SET @amount = 0;SET @rank = 1;SET @shunxu = 0;SELECT tmp2.id as id,tmp2.name as name,tmp2.amount as amount,tmp2.rank as rankFrom (SELECT tmp.id as id,tmp.name as name,tmp.amount as amount, @shunxu: [Email protected]+1,if (email protected], @rank,

There are 5 Mysql aggregation functions:1, COUNT () Number of records2, max () maximum value3, min () minimum value4, AVG () average5, sum () sumAggregation functions often work with groups.1. Create a groupSelect Name, Max (age) from Stu Group by

1. Selection: SELECT * from table name where condition2. Insert: INSERT into table name (Field 1, Field 2) VALUES (value 1, value 2)3. Delete: Delete from table name where condition4. Updated: Update table name SET field = value Where condition5.

The MySQL version used here is 5.6.23 and is configured with a new MySQL master-slave copy (no data existed before)1. Configure MasterVI My.cnflog-bin=mysql-binserver-id=1innodb_flush_log_at_trx_commit=1sync_binlog=1service mysqld Restart2.

1. Install MySQL　　Yum Install mysql-server mysql-devel2. Start MySQL// Start // Restart // Stop grep // view MySQL Service status3. Create a MySQL account' 123 '4. Go to MySQLMysql-uroot-p1235. Create an account from the server used to access the

Install mysql Community version in Centos7 development environment, centos7mysql1. Install mysql on Centos7 The first server to be developed is centos7, and the default database installed above is MariaDB.There is another difference. To install