Category:DBT

  • Redis5 cluster related commands of redis service

    Time:2021-1-20

    The last blog mainly talked about the following redis.trib.rb This tool is used to manage the nodes in redis3 / 4 cluster. For a review, please refer tohttps://www.cnblogs.com/qiuhom-1874/p/13456915.htmlToday, let’s talk about the description of cluster related configuration commands on redis5; Creating clusters [[email protected] redis]# redis-cli -a admin –cluster create 192.168.0.41:6379 192.168.0.42:6379 192.168.0.43:6379 192.168.0.41:6380 192.168.0.42:6380 192.168.0.43:6380 […]

  • Read optimistic lock and pessimistic lock and mvcc in database

    Time:2021-1-20

    preface In the actual use of the database, we often encounter situations in which we do not want the data to be written or read at the same time. For example, in the second kill scenario, two requests read to the system at the same time, and there is one inventory in the system, and […]

  • Database maintenance

    Time:2021-1-20

    affair The object of database concurrency control Transaction is the logical work unit of database The operations in the sequence are either all done or none done   characteristic; Atomicity All operations in a transaction are indivisible, either executed or not executed. This is the atomicity of a transaction. uniformity A successful transaction must be […]

  • Oracle database optimization skills (1)

    Time:2021-1-20

    Oracle database optimization skills (1) 1. Join order in where clause In Oracle database, the execution order of where clause isBottom upAccording to this principle, the connection between tables must be written before other where conditions, and those conditions that can filter out the maximum number of records must be written before other where conditions […]

  • MySQL learning notes (19): optimizing database objects

    Time:2021-1-20

    This article is updated on August 18, 2019, using MySQL 5.7 and operating system deepin 15.4. catalog Data type of optimization table Improve the efficiency of table access by splitting Inverse normalization Using intermediate table to improve the efficiency of statistical query Once the database object is designed and put into use, it is troublesome […]

  • Handling method of MySQL numeric type overflow

    Time:2021-1-20

    Let’s ask you a question. What happens when a column is set to int (0) in MySQL? To illustrate this problem, we need to create a table first DROP TABLE IF EXISTS `na`; CREATE TABLE `na` ( n1 INT(0) NOT NULL DEFAULT ‘0’, n2 INT(11) NOT NULL DEFAULT ‘0’ ); Then we use the following […]

  • The usage of raiserror function in SQL Server database

    Time:2021-1-20

    The usage of raiserror function in SQL Server database serverdatabaseThe function of raiserror in ASP.NETLike throw new exception in, it is used to throw an exception or error. This error can be caught by the program. The common format of raiserror is as follows:Raiserrror (‘error description ‘, error severity code, error identification, parameter values in […]

  • Summary after reading MySQL (3)

    Time:2021-1-19

    A series of articles: Summary after reading MySQL Summary after reading MySQL (2) Summary after reading MySQL (3) There is something wrong with the master library. What about the slave library? The basic one master multi slave structure is as follows In the figure, the dashed arrow indicates the master-slave relationship, that is, a and […]

  • Java redis Series 2 (installation and use of redis + implementation of redis persistence))

    Time:2021-1-19

    Java redis Series 2 (installation and use of redis + implementation of redis persistence) What is redis? Redis is an open source and high-performance key value database developed with C language. It officially provides test data, and 50 requests execute 100000 requests concurrently. The read speed is 110000 times / s, and the write speed […]

  • SQL Server special character query and use of escape

    Time:2021-1-19

    An old project of the company, SQL Server In fuzzy query, the query condition contains, and then the query result is always empty If there is no character after escape character in like mode, the mode is invalid and like returns false. If the character after the escape character is not a wildcard, the escape […]

  • Springboot learning notes 0.1

    Time:2021-1-19

    Springboot learning notes Introduction to spring boot 1、 Springboot comparison Spring framework The core features of spring framework are dependency injection (DI) and inversion of control (IOC). If you can reasonably use Di and IOC, you can develop loosely coupled and well extensible applications. Spring MVC Spring MVC provides a friendly way to develop web […]

  • DQL query statement

    Time:2021-1-19

    Sort query*Syntax: order by clause*Order by sort field 1, sort method 1, sort field 2, sort method 2 *Sort by: *ASC: ascending order, default. *Desc: descending order. *Note: *If there are multiple sorting conditions, the second condition will be judged only when the condition values of the current edge are the same. Aggregate function: a […]