掌握Rust编程：SQLite入门指南

[dependencies]rusqlite = "0.29"

// rusqlite_demo/src/main.rsuse std::io;use std::io::BufRead;use rusqlite::Error;use rusqlite::{Connection};const CREATE_TABLE: &str = "CREATE TABLE IF NOT EXISTS books                             (id INTEGER PRIMARY KEY,                            title TEXT NOT NULL,                            author TEXT NOT NULL,                            year INTEGER NOT NULL)";#[derive(Debug)]struct Book {    id: u32,    title: String,    author: String,    year: u16,}fn extract_ok(p: Result<Book, Error>) -> Option<Book> {    if p.is_ok() {        Some(p.unwrap())    } else {        None    }}fn insert(conn: &Connection) {    let stdin = io::stdin();    let lines = stdin.lock().lines();    for line in lines {        let elems = line.unwrap();        let elems: Vec<&str> = elems.split(",").collect();        if elems.len() > 2 {            let _ = conn.execute(                "INSERT INTO books (id, title, author, year) VALUES (?1, ?2, ?3, ?4)",                &[&elems[0], &elems[1], &elems[2], &elems[3]],            );        }    }}fn init_database(conn: &Connection) {    conn.execute(CREATE_TABLE, ()).unwrap();}fn query(conn: &Connection) {    let mut stmt = conn        .prepare("SELECT id, title, author, year FROM books WHERE year >= ?1")        .unwrap();    let movie_iter = stmt        .query_map(&[&2013], |row| Ok(Book {            id: row.get(0)?,            title: row.get(1)?,            author: row.get(2)?,            year: row.get(3)?,        }))        .unwrap();    for movie in movie_iter.filter_map(extract_ok) {        println!("Found book {:?}", movie);    }}fn main() {    let conn = Connection::open("./books").unwrap();    init_database(&conn);    insert(&conn);    query(&conn);}