Programmer Think

Start and stop of service When GBase 8a is installed, GBase.com The server service needs to be started manually. After that, whenever the machine is powered on and restarted, GBase All server services need to be started manually. If the user needs to manually start and stop the GBase service during use, the user who installed GBase 8A should b ...

1, View 1. Concept View is to wrap a more complex query statement in the view to simplify the statement. Views are stored in the database and can be reused. Data is not stored in the view. The data of the view exists in the base table of the view and changes based on the change of the table data. 2. Why use views? In order to facilitate ...

MongoDB RDBMS vs NoSQL RDBMS -Highly organized structured data -Structured query language (SQL) -Data and relationships are stored in separate tables. -Data manipulation language -Strict consistency -Basic transaction NoSQL -Represents more than just SQL -No declarative query language -There are no predefined patterns Key value pair storage ...

preface I'm going to open a new series, which is a new field I haven't touched much before, called performance tuning. When I read the word "performance tuning" when I was brushing my blog, I was stunned and felt that time had stagnated. I found that I didn't know the performance level of the project code I wrote. Even if it ...

Cluster planning HostIPfunctioncentos01192.168.52.221mastercentos02192.168.52.222segmentcentos03192.168.52.223segment It is a cluster composed of three machines in total, and the standby node is not set up System environment nameexplainoperating systemCentos7GreenplumGreenplum 6.17JavaJDK8GCCGCC 4.8.5 Modify system files Modify the system r ...

The difference between Oracle and Mysql 1, Main differences 1. Software specification: Oracle is a large database, which occupies a lot of memory;Mysql is a lightweight database, which is lightweight and occupies less memory; ps: I pulled the image of the two with docker. mysql is 545M in size, while oracle11g requires 6.85G 2. Expenses: ...

Recently, I saw a literature that used the data in GBD database to predict the development trend of disease burden. I found it very interesting, so I took the time to repeat the key methods in R language. reference: Changing trends in the disease burden of esophageal cancer in China from 1990 to 2017 and its predicted level in 25 years DOI: 10 ...

catalogue 1. Construction project 1. Build experimental database 2. Import relevant jar packages 3. Create a configuration file for mybatis 4. Create a tool class for the key objects SqlSessionFactory and SqlSession of mybatis 5. Build entity class 6. Interface 7. mapper file 8. Directory structure diagram "Check" operation ...

1. Parent child inheritance tableAt present, MogDB does not support inherits inheritance feature.omm=# CREATE TABLE tab_t2(age int) inherits(tab_t1); ERROR: CREATE TABLE ... INHERITS is not yet supported.PostgreSQL supports inheritance. Partitioned tables before version 10 are implemented through inheritance. Each partition is actually an inde ...

1. Complex mapping 1.1 result mapping 1.1.1 basic concepts resultType: if the attribute name of the entity is consistent with the field name in the table, the query results will be automatically encapsulated into the entity classResutlMap: if the attribute name of the entity is inconsistent with the field name in the table, you can use Resut ...