MySQL と Go 言語を使用してシンプルな投資および財務管理システムを開発する方法

CREATE TABLE IF NOT EXISTS user (
    id INT AUTO_INCREMENT PRIMARY KEY,
    username VARCHAR(255) NOT NULL,
    password VARCHAR(255) NOT NULL,
    email VARCHAR(255) NOT NULL,
    balance DECIMAL(10, 2) DEFAULT 0.0
);

package main

import (
    "database/sql"
    "fmt"
    "log"

    _ "github.com/go-sql-driver/mysql"
)

const (
    DBUsername = "root"
    DBPassword = "password"
    DBHost     = "localhost"
    DBPort     = "3306"
    DBName     = "investments"
)

func main() {
    // 连接数据库
    db, err := sql.Open("mysql", fmt.Sprintf("%s:%s@tcp(%s:%s)/%s", DBUsername, DBPassword, DBHost, DBPort, DBName))
    if err != nil {
        log.Fatal(err)
    }
    defer db.Close()

    // 注册用户
    registerUser(db, "john", "password123", "john@example.com")

    // 登录
    user, err := loginUser(db, "john", "password123")
    if err != nil {
        log.Fatal(err)
    }
    fmt.Printf("Welcome, %s!
", user.Username)
}

// 注册用户
func registerUser(db *sql.DB, username, password, email string) error {
    stmt, err := db.Prepare("INSERT INTO user (username, password, email) VALUES (?, ?, ?)")
    if err != nil {
        return err
    }
    defer stmt.Close()

    _, err = stmt.Exec(username, password, email)
    return err
}

// 登录
func loginUser(db *sql.DB, username, password string) (*User, error) {
    var user User
    row := db.QueryRow("SELECT * FROM user WHERE username = ? AND password = ?", username, password)
    err := row.Scan(&user.ID, &user.Username, &user.Password, &user.Email, &user.Balance)
    if err != nil {
        return nil, err
    }
    return &user, nil
}

type User struct {
    ID       int
    Username string
    Password string
    Email    string
    Balance  float64
}

CREATE TABLE IF NOT EXISTS investment (
    id INT AUTO_INCREMENT PRIMARY KEY,
    name VARCHAR(255) NOT NULL,
    amount DECIMAL(10, 2) NOT NULL,
    user_id INT,
    FOREIGN KEY (user_id) REFERENCES user (id)
);

// 发布项目
func createInvestment(db *sql.DB, name string, amount float64) error {
    stmt, err := db.Prepare("INSERT INTO investment (name, amount, user_id) VALUES (?, ?, ?)")
    if err != nil {
        return err
    }
    defer stmt.Close()

    _, err = stmt.Exec(name, amount, userID)
    return err
}

// 购买项目
func buyInvestment(db *sql.DB, investmentID, userID int) error {
    // 检查用户余额是否足够
    var balance float64
    row := db.QueryRow("SELECT balance FROM user WHERE id = ?", userID)
    err := row.Scan(&balance)
    if err != nil {
        return err
    }
    if balance < investmentAmount {
        return fmt.Errorf("Insufficient balance")
    }

    // 扣除购买金额
    _, err = db.Exec("UPDATE user SET balance = balance - ? WHERE id = ?", investmentAmount, userID)
    if err != nil {
        return err
    }

    // 将用户与投资项目关联
    _, err = db.Exec("UPDATE investment SET user_id = ? WHERE id = ?", userID, investmentID)
    return err
}