Category:MySql

  • Solve the problem of MySQL login 1045 under CentOS

    Time:2020-4-2

    Because the whole application needs to be deployed under CentOS, the operation of database is indispensable. But many people may encounter some problems, such as the success of creating users, but they cannot log in. There are generally two reasons for not being able to log in. First, the remote access port is not open. […]

  • Common SQL writing and optimization

    Time:2020-4-2

    Common SQL optimization methods To optimize the query, we should try to avoid full table scanning. First, we should considerWhere and order by。 Should tryavoidIn the where clause, theNull value judgmentOtherwise, the engine will discard the index and scan the whole table, such as: select id from t where num is null You can set […]

  • Timeout of zookeeper request in Dubbo: configuration of mybatis + spring connection to mysql8.0.15

    Time:2020-4-1

    I’m going to review Java in these two days, So write a shopping mall project with Dubbo to practice, but on the first test of the card, start the provider service and the consumer service, but the request interface always reports the timeout error of the zookeeper request (Dubbo + zookeeper server repeatedly calls three […]

  • Getting started with databases

    Time:2020-4-1

    Knowledge points △ reasons for using database 1 complexity of file operation2 synchronization3 concurrent processing4 safety △ database system (DBS)Database (DB) + database management system (DBS) + database application + Database Administrator (BDA) + end user △ database management system dBmNetwork application serverWe are going to use data from the server – we need to […]

  • Mysql8.0 uses window function to solve sorting problem

    Time:2020-3-31

    Introduction to MySQL window functions MySQL supports window functions from 8.0, which are already supported in most commercial databases and some open source databases, some of which are also called analysis functions. What is a window? The concept of window is very important. It can be understood as a set of records. Window function is […]

  • MySQL event history

    Time:2020-3-31

    demand The job history records of SQL server are saved in MSDB database, which is convenient to query the relevant job definitions, plans and history records, while the events of MySQL have no history records. In order to check whether the event executes normally and the execution results, the following two steps are used to […]

  • Detailed explanation of MySQL account management principle and implementation method

    Time:2020-3-30

    This paper introduces the principle and implementation of MySQL account management. To share with you for your reference, as follows: Account management When operating the database in the production environment, it is absolutely not allowed to use the root account to connect, but to create a specific account, grant the specific operation authority to the […]

  • MySQL Cluster highly available

    Time:2020-3-30

    Catalog MySQL highly available Galera cluster Galera Cluster Galera cluster features Disadvantages of Galera cluster Galera cluster working process Official document of Galera cluster Galera cluster consists of two components Wsrep replication implementation PXC principle PXC most commonly uses the following four port numbers: Important concepts and core parameters involved in PXC: Practical case: percona […]

  • Detailed explanation of mysql8.018 installation and configuration on Linux

    Time:2020-3-29

    Installation introduction under Windows: go and have a look at mysql8.018 installation introduction under Windows Linux platform: Take MySQL 8.0.18, Ubuntu 16.04.6 lts (GNU / Linux 4.4.0-142-generic x86_) as an example: A. Automatic installation sudo apt-get install mysql-server sudo apt-get install mysql-client sudo apt-get install libmysqlclient-dev B. Download the installation package and install the DEB […]

  • MySQL 5.7 multiple instances

    Time:2020-3-29

    In this paper, mysql5.7 is used to implement multiple instances, and the ports are 3306 and 3307. 1. Multi instance natureOpen multiple MySQL service ports (33063307) and run multiple MySQL service processes on one machine. These service processes provide their own services by listening to different service ports through different sockets; Multiple instances share a […]

  • Detailed steps of installing MySQL with cluster rpm

    Time:2020-3-28

    Install MySQL database a) Download MySQL source installation package: WGet http://dev.mysql.com/get/mysql57-community-release-el7-8.noarch.rpm b) Install MySQL source: Yum localinstall mysql57-community-release-el7-8.noarch.rpm If complete! Appears at the end, the MySQL source installation is complete c) Check whether the installation is complete: Yum repolist enabled| grep “mysql. * – community. *” d) Install MySQL: Yum install MySQL community server If […]

  • How to query the result by another time field in the case of grouping?

    Time:2020-3-28

    If there is such a table: The script is as follows: DROP TABLE IF EXISTS `jl_site_operation`;CREATE TABLE `jl_site_operation` ( `id` int(11) NOT NULL AUTO_INCREMENT,`Site [ID ` int (11) default null comment ‘station ID’,`Param_id ` int (11) default null comment ‘parameter ID (associated jl_parameter_config table ID)’,`Param_value ` varchar (255) default null comment ‘the value corresponding to […]