Are MySQL Join statements inefficient?

We often hear Join join queries that avoid using MySQL because of poor performance. Is this the case?Let's try it out. 1. Environment MySQL: 5.7.30 Storage Engine: InnoDB Index type: default optimized B+tree   2. Prepare 2.1 Table preparation and data preparation We plan to create five tables and insert 10W pieces of data into them, ...

Posted on Tue, 02 Jun 2020 07:53:10 -0400 by hanpedro

Oracle learning - view, sequence, synonym, index

1. View 1.1 what is a view View is a mapping of virtual table and entity table. When to use views In development, there are some table structures that do not want too many people to contact, so entity tables are mapped to a view. (simplified table structure) In the project process, programmers mainly focus on the performance of coding and ...

Posted on Mon, 01 Jun 2020 11:55:47 -0400 by ldtiw

flowable-6.5.0 running official demo

1. Download flowable-6.5.0 from the official website: https://flowable.com/open-source/downloads/ After downloading and unzipping, open the directory wars 2. Find a clean tomcat8 In the war file directory flowable-admin.war  flowable-idm.war  flowable-modeler.war  flowable-rest.war  flowable-task.war A total of 5 war packages are placed in ...

Posted on Mon, 01 Jun 2020 11:10:09 -0400 by krelian

[scheme optimization] 1. OpenResty combined with Lua and Redis to realize the strategy of high request concurrency

catalog 1, Overall architecture description 1.1 scheme v1.0 1.2 scheme v1.0 optimization 1.3 scheme comparison 2, Scenario 2.0 deployment 2.1 OpenResty installation 2.2 Lua scripting 2.3 configure OpenResty 3, Testing 1, Overall architecture description 1.1 scheme v1.0 Before optimizing the old design framework, take a look at co ...

Posted on Mon, 01 Jun 2020 05:00:28 -0400 by gabriel kent

type column parsing of explain

1,const Indicates that the execution step returns at most one row of data. const usually appears in the equivalent query of the primary key or unique index, such as the equivalent query of the primary key id of the t table:It can be considered that it is as fast as a rocket to locate a record by comparing the equivalence between the primary key ...

Posted on Sun, 31 May 2020 11:54:35 -0400 by peter_anderson

mysql count(*) count count(id) explanation

Environment wins10 8g memory mysql5.7.27 mysql my.ini Configuration note (innodb_flush_log_at_trx_commit=0) configuration [Client] #Set 3306 port port = 3306 [mysqld] #Set 3306 port port = 3306 # Set the installation directory of mysql basedir=E:devmysql-5.7.27-winx64 # Set the storage directory of mysql database data datadir=E:devmysql-5.7.2 ...

Posted on Sun, 31 May 2020 10:10:15 -0400 by cofey12681

Asp.Net MVC based on Fleck's development of multi person web chat room

1, Core description of the project 1. Fleck is a relatively simple third-party component to implement websocket, which does not need to install additional containers. There are also several interfaces available. 2. The project is based on. net framework 4.7.2, developed on vs2019, and has not tried to run on the lower version. However, the new ...

Posted on Sun, 31 May 2020 07:58:00 -0400 by Haroskyline

Asp.Net MVC based on Fleck's development of multi person web chat room

1, Core description of the project 1. Fleck is a relatively simple third-party component to implement websocket, which does not need to install additional containers. There are also several interfaces available. 2. The project is based on. net framework 4.7.2, developed on vs2019, and has not tried to run on the lower version. However, the new ...

Posted on Sun, 31 May 2020 07:36:17 -0400 by adrian28uk

Spring Data Rest encounters a composite primary key

If the project persistence layer uses Spring Data JPA and some data tables contain composite primary keys (Union primary keys), how can the interface generated by Spring Data Rest access the data corresponding to a primary key in these data tables? Suppose the database has two data tables film with compound primary key ...

Posted on Sun, 31 May 2020 06:05:01 -0400 by rathlon

Summary of JDBC basic knowledge

Refer to the summary of Java language programming foundation version 10 Main interface 1 Basic JDBC program 2. The main methods of initializeDB and showGrade are to access the database from JavaFX Statement 1PreparedStatement interface inherits from Statement interface to create parameterized SQL Statement Exa ...

Posted on Sun, 31 May 2020 04:35:47 -0400 by cpharry