MySQL

MySQL InnoDB supports three kinds of line locking methods:Row lock (Record Lock): The lock is added directly above the index record.Gap Lock: Locks are added to a nonexistent free space, which can be between two index records or the space after the

ObjectiveAfter the completion of the table, it is obvious that the query for the data becomes more complex, especially in relation to the table, and in some cases it is not possible to use join at all.In fact, the individual is more encouraged to

Basic commandsDESC table name; query table structureShow columns from table name; query table resultsHaving the use, either out of the lookup field (select) or within the aggregation function (sum (); count ();.Limet 2,2: The result of the lookup is

I. File-based verification of virtual users① Create a virtual user database file. Command: Vim/etc/vsftpd/viruser650) this.width=650; "src=" Https://s4.51cto.com/oss/201710/27/327cf87fecda172d1fbabe943fefd138.png "title=" 1.png " alt= "327cf87fecda17

Triggers in MySQLTrigger Requirements: There are two tables, an order form, a commodity table. Each order is generated, the inventory of goods is reduced accordingly. Trigger (Trigger) Binding a piece of code in advance for a

MySQL Connection- - penter Password: ******The mysql> Command Prompt window will appear after successful login to The MySQL monitor....mysql >Create a database after logging inCREATE DATABASE IF not EXISTS DatabaseName;Deleting a databaseDROP

The InnoDB engine provides transactional security with commit, rollback, and crash resiliency, but the contrast MyISAM engine is less efficient and consumes more disk space and preserves data and indexes1. Auto-Grow columnThe auto-grow column of the

View current MySQL storage engine: Show engines \g or show variables like ' have% ';　　Both of these methods see which storage engines are supported by the current database, where disavled records indicate support for the storage engine, but are

Environment:10.0.0.51/172.16.1.51 mysql01 main Repository CentOS 7.210.0.0.52/172.16.1.52 mysql02 relay from the library CentOS 7.210.0.0.53/172.16.1.53 mysql03 from the library CentOS 7.2MYSQL01 configuration:[Mysqld]Bind-address =

1. Download the MySQL repo sourcewget https://repo.mysql.com//mysql57-community-release-el7-11.noarch.rpm2, installation SourceYum Localinstall xx.rpm3, install MySQLYum Install Mysql-community-server4. Start MySQLService mysqld Start5. View

MySQL master-slave synchronization:1. Why the master-slave synchronization?In Web application system, database performance is one of the main causes of system performance bottleneck. Especially in large-scale systems, database clustering has become

Isolation level of the transaction:　　READ UNCOMMITTED (UNCOMMITTED)At this level, the changes in the transaction, even if not committed, are visible to other transactions, and the transaction can read uncommitted data.　　Read COMMITTED (submit

What is MDLMdl,meta data lock, a metadata lock, is generally called a dictionary lock. The dictionary lock corresponds to a data lock. Dictionary lock is to protect the data object is changed, usually some DDL will change the Dictionary object, such

Online DDL consists of 3 stages, prepare phase, DDL execution phase, commit phase, rebuild mode is more than No-rebuild mode in a DDL execution phase, prepare phase and commit phase are similar. The following is a main introduction to the three

MySQL declaration variables and stored procedure analysis, mysql Stored Procedure Declare Variables Set global variables Set @ a = 'new variable '; Declear variables used in functions and stored procedures Declear a int unsigned default 1; This type

Analysis of mysql union and union all, analysis of mysqlunionall In the database, the UNION and union all keywords combine the two results into one, but both have different usage and efficiency. UNION in MySQL UNION filters out duplicate records

Code example of the Order By multi-field sorting rule in MySQL, mysqlorder Mentioned above A whimsy, want to know what rules mysql order by sorting is based on? Okay. If you don't have much to say, go to the topic. MySql order by single Field Create

MySQL removes spaces from a field in batches. mysql fields contain spaces. Is there any way for Mysql to remove spaces in characters in a field in batches? It is not only a space before and after the string, but also a space in the middle of the

Details about how to clear table space fragments in MySQL. How to clear table space fragments in MySQL Causes of fragmentation (1) the storage of a table is fragmented. When a row of content is deleted, the space in the row is blank and left blank.

Mysql master-slave synchronization configuration and mysql master-slave Synchronization 1. Install mysql on two Ubuntu machines1. Check whether mysql is installed in the system. This is already installed Run the preceding command if no