Go言語を使用したMySQLデータベースのデータ操作の事前検証

import ( "database/sql" "fmt" _ "github.com/go-sql-driver/mysql" ) func main() { // Open up our database connection. db, err := sql.Open("mysql", "user:password@tcp(127.0.0.1:3306)/database") if err != nil { log.Fatal(err) } // Verify the connection with the Ping() method. if err := db.Ping(); err != nil { log.Fatal(err) } // Do something with the newly opened connection here. // ... }

func insertData(db *sql.DB, username string, password string) error { // Ensure username and password are not empty. if len(username) == 0 || len(password) == 0 { return errors.New("username and password are required") } // In the real world, ensure the username doesn't exist before creating a new user. if userExists(db, username) { return errors.New("user already exists") } // Perform the insert operation. _, err := db.Exec("INSERT INTO users (username, password) VALUES (?, ?)", username, password) if err != nil { return err } return nil } func userExists(db *sql.DB, username string) bool { // Prepare the SQL statement. stmt, err := db.Prepare("SELECT count(*) FROM users WHERE username = ?") if err != nil { return false } defer stmt.Close() // Execute the SQL statement. var count int err = stmt.QueryRow(username).Scan(&count) if err != nil { return false } return count > 0 }

func getUsers(db *sql.DB, username string) ([]User, error) { // Ensure the username parameter is not empty. if len(username) == 0 { return nil, errors.New("username is required") } // Prepare the SQL statement. stmt, err := db.Prepare("SELECT * FROM users WHERE username = ?") if err != nil { return nil, err } defer stmt.Close() // Execute the SQL statement with the given username parameter. rows, err := stmt.Query(username) if err != nil { return nil, err } defer rows.Close() // Collect the query results into a slice of User objects. var users []User for rows.Next() { var u User err := rows.Scan(&u.Username, &u.Password) if err != nil { return nil, err } users = append(users, u) } return users, nil }