Programmer Think

4.3 data definition 4.3. 1 Definition and deletion of mode What is a database schema? Database schema is a logical grouping object. Database schema is a collection of database objects, which contains various tables, views, stored procedures, indexes, etc. Imagine a schema as a container for objects. Database schema can be used as a namespace ...

1, Understanding of Stream Stream is a key abstract concept for processing collections in Java 8. It can specify the operations you want to perform on collections, and can perform very complex operations such as finding, filtering and mapping data.Use the Stream API to operate on collection data, similar to database queries executed using ...

1. Concept of database DB: database: a "warehouse" for storing data. It holds a series of organized data;DBMS: Database Management System. Database is a container created and operated by DBMS;SQL: Structure Query Language: a language specially used to communicate with the database;Relationship diagram of the three: 2. Common ...

The historical data of Lotto and lottery are public data, and there are no legal obstacles. We select the data of the public website and save it as csv, excel and other format data files, which is convenient for secondary data sorting. The whole process is mainly divided into obtaining the web page (finding the effective login of the web site ...

The basic steps for using a JDBC transaction are as follows: @Test public void testTX(){ String url = "jdbc:mysql://127.0.0.1:3306/test"; String username = "root"; String password = "1234"; String sourceUserId = "leo"; String desUserId = "xnn"; int money = 500; Connection connection = null; try { //1. ...

Due to the learning needs, I will start to learn the basic knowledge of database and the preparation and use of SQL statements from today. Therefore, I record my learning process here to urge myself, consolidate the knowledge I have learned, and hope to help more introductory students. 1. Establish database create database db_name;//db_name i ...

Joint query of Mysql union of joint query union can merge tables queried by more than two select statements and eliminate duplicate rows in the table. The select statement needs to have the same number of columns with the same data type. 1. Query the ID and province name of each province in China select ProID,ProName from T_Province 2. I ...

github address of GreenDaoGreen Dao's Google discussion areaGreenDao encrypted SQLCipher for Android official description addressDocuments used by GreenDao The role of GreenDao? Through GreenDao, we can operate the database more quickly. We can use a simple face object API to store, update, delete and query Java objects. Advantages and disad ...

mysql application: 1.client: client program, which connects to the server 2.SQLyog is easy to use and can be executed directly from multiple command lines. 3. Send e-mail: the default port is net25. The default port of the database is 3306. This port is unified according to the port of the server 4.server side: on linux. show databases; Displa ...

It's not difficult to grab public data from Wikipedia, Baidu Encyclopedia and other websites in Python and store them in tables. However, in many application scenarios, we are no longer limited to storing the captured data in tables, but also need to be more intuitive to visualize. For example, in this case, Python is used to capture the cities ...