Operation code for database part knowledge using JAVA

This week, we first temporarily ended the advanced knowledge of java and entered the study of database:

Advanced part of java:
          1. Multi-threading: Thread concurrency (multiple threads operate shared variables) ;
lock mechanism, keywords are synchronize (safety, lock objects and methods), WAIT, notify
(pessimistic) dead lock, wait, notify, notifyall;
2. Network programming: UDP data broadcast (the data sender only needs to send one copy to the switch, and the switch is responsible for making n copies of this information and sending it to all machines)
                                     Http Protocol (HyperText Transfer Protocol)
                           Json data format, syntax rules: JSON Object {"attribute name": "Attribute value"}
json array ["Element 1", "Element 2" ...]
JSON plug-in: -JSON-LIB
- Gson ##- Jackson
- Fastjson -Alibaba
;
database part: (using MySQL5.5 database, and Navicat graphics tools to operate)
3. System and MySQL commonly used command
system commands (with by the Run as administrator)

: #Start service

net start mysql

                                                                                                                                                                                                  ’s ’s ’s ’ s ’ s ’ ‐     ‐   ‐   ‐ ‐‐ ‐‐ net stop mysql


                                                               
mysql -uroot -p password

                                                                                                                                                                  

#                                                                                                                                                                                                                                                             Backup database instance mysqldump -uroot -proot mydb > d:/mydb.sql
                                                                                                                                                                        ’ s ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ d:/mydb.sql to uroot -proot mydb tbuser > d:/tbuser.sql  
                 

Mysql common commands

:-Show the database instance
Show databases;

-Create the database instance
Create database Mydb;

-Display all database tables in the instance
Show Tables;
## SQL statement

# Auto_increment: Set up columns, which can be used for the primary key column and the unique column of non -air (not null unique)

                                                                                                                                                                                                                                                                                       ​​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​When defining the length, add 0 to the front of the value)

, alter, drop

                                                                                                         . Language: control authority) revork, grant;

                5. (Integrity Conditions) Constraints: 1. Primary key constraint
2. Foreign key constraint

3. Not empty constraint

4. Unique constraint
5. Check constraint (mysql does not support it yet)

                                                                                                                                                                                                                                          .         FROM target table


                                                                                                                                                                                                                                     ​ 


【GROUP BY column Name】

## [HAVING Query Conditions]

## 【Order By column name ASC | Desc】

                                                【LIMIT [偏移行,]记录行数】
  
                                              单表查询：模糊查询（“%”，“_”），聚合函数
                                              多表查询：等值连接，外连接
                                              mysql函数的使用。

import java.io.Serializable;

/**
 * 工作详情类
 * @author NIUXUYUAN
 */
public class Jobs implements Serializable{

    /**
     *
     */
    private static final long serialVersionUID = 1L;
    private String id;          //id
    private String experience;  //工作经验
    private String city;        //工作地点
    private String industry;    //行业
    private String detail;      //工作详情
    private String company;     //公司
    private String jobname;     //职位
    public Jobs(String id, String experience, String city, String industry, String detail, String company,
            String jobname) {
        super();
        this.id = id;
        this.experience = experience;
        this.city = city;
        this.industry = industry;
        this.detail = detail;
        this.company = company;
        this.jobname = jobname;
    }

    @Override
    public String toString() {
        return "Jobs [id=" + id + ", experience=" + experience + ", city=" + city + ", industry=" + industry
                + ", detail=" + detail + ", company=" + company + ", jobname=" + jobname + "]";
    }

    public String toString(int i) {
        return experience+city+industry+detail+company+jobname;
    }

    public Jobs() {
        // TODO Auto-generated constructor stub
    }

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getExperience() {
        return experience;
    }

    public void setExperience(String experience) {
        this.experience = experience;
    }

    public String getCity() {
        return city;
    }

    public void setCity(String city) {
        this.city = city;
    }

    public String getIndustry() {
        return industry;
    }

    public void setIndustry(String industry) {
        this.industry = industry;
    }

    public String getDetail() {
        return detail;
    }

    public void setDetail(String detail) {
        this.detail = detail;
    }

    public String getCompany() {
        return company;
    }

    public void setCompany(String company) {
        this.company = company;
    }

    public String getJobname() {
        return jobname;
    }

    public void setJobname(String jobname) {
        this.jobname = jobname;
    }

}

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.ArrayList;
import java.util.List;

public class AddJobs {

    static List<Jobs> list = new ArrayList<>();
    File file = new File("jobs");

    /**
     * 输入数据
     * @throws IOException
     */
    public void input() throws IOException {
         BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
         System.out.println("以id/experience/education/city/industry/detail/company/jobname格式填入：");
         String msg = "";
         while(!(msg = br.readLine()).equalsIgnoreCase("quit")) {
             add(msg);
         }
         br.close();
    }

    /**
     * 将数据变为Jobs对象存入list集合
     * @param msg
     */
    private void add(String msg) {
        String[] s = msg.split("/");
        Jobs job = new Jobs(s[0], s[1], s[2], s[3], s[4], s[5], s[6]);
        list.add(job);
    }

    private void checkFile() throws FileNotFoundException, IOException, ClassNotFoundException {
        if(file.length()>0) {
        ObjectInputStream ois = new ObjectInputStream(new FileInputStream(file));
        List<Jobs> temp = (List<Jobs>)ois.readObject();
        if(temp!=null) {
            list.clear();
            for(Jobs t:temp) {
                list.add(t);
            }
        }
        ois.close();
        }
    }
    public static void main(String[] args) throws FileNotFoundException, IOException, ClassNotFoundException {
        AddJobs aj = new AddJobs();
        if(!aj.file.exists()) {
            aj.file.createNewFile();
        }
        aj.checkFile();
        aj.input();
        ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream(aj.file));
        oos.writeObject(list);
        oos.close();
    }

}

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.ObjectInputStream;
import java.util.ArrayList;
import java.util.List;

public class Query {

    static List<Jobs> list = new ArrayList<>();
    File file = new File("jobs");

    /**
     * 查看file文件，将数据导入list集合
     * @throws FileNotFoundException
     * @throws IOException
     * @throws ClassNotFoundException
     */
    private void checkFile() throws FileNotFoundException, IOException, ClassNotFoundException {
        if(file.length()>0) {
        ObjectInputStream ois = new ObjectInputStream(new FileInputStream(file));
        List<Jobs> temp = (List<Jobs>)ois.readObject();
        if(temp!=null) {
            list.clear();
            for(Jobs t:temp) {
                list.add(t);
            }
        }
        ois.close();
        }
    }

    public void check() throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        System.out.println("请输入experience/education/city/industry/detail/company/jobname的某些信息");
        String msg = br.readLine();
        String[] s = msg.split("/");
        String regex = "";
        for (String str : s) {
            regex += "[\\s\\S]*" + str + "[\\s\\S]*";
        }
        List<Jobs> temp = new ArrayList<>();
        for (Jobs j : list) {
            msg = j.toString(1);
            if(msg.matches(regex)) {
                temp.add(j);
            }
        }
        System.out.println("结果");
        for (Jobs jobs : temp) {
            System.out.println(jobs);
        }
    }
    public static void main(String[] args) throws FileNotFoundException, ClassNotFoundException, IOException {
        Query q = new Query();
        q.checkFile();
        q.check();
    }
}

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