use mysql::*;
use mysql::prelude::*;
use serde::Serialize;
use serde::Deserialize;
#[derive(Debug, PartialEq, Serialize, Deserialize)]
pub struct Bookdata {
pub id: u64,
pub title: String,
}
#[tokio::main]
async fn main() {
// connect to the database
let url = "mysql://<URL>";
let opts = Opts::from_url(url).unwrap();
let pool = Pool::new(opts).unwrap();
let mut conn = pool.get_conn().unwrap();
//// GET DATA FROM DATABASE
let selected_results = conn
.query_map(
"SELECT id, title FROM books",
|(id, title )| {
Bookdata {id, title}
},
);
println!("{:?}", selected_results);
// for d in selected_results.iter() {
// println!("{:?}: {:?}", d.id, d.title);
// }
//// END GET DATA FROM DATABASE
}
This works. it prints out every id and title from the database in a json format.
when i uncomment the {:?} line i get an error that no valid field for id and title exist on struct bookdata:
error[E0609]: no field title on type &Vec<Bookdata>
ultimatly, i want to put the id and title into a csv file, i have found that there's a csv crate but most examples are about reading from/to CLI. i have yet to find a tutorial about grabbing data from mysql and put it into a csv file.
i saw that one but since i cant get the fields from the database, i see not how i can write it to csv
otherwise i cpould use something like:
let mut wtr = csv::Writer::from_writer(&selected_results);
// When writing records with Serde using structs, the header row is written
// automatically.
wtr.serialize(Record {
id: &selected_results.id.to_string(),
title: &selected_results.title.to_string(),
});
wtr.flush()?;
use mysql::*;
use mysql::prelude::*;
pub struct bookdata {
pub id: u64,
pub title: String,
}
#[tokio::main]
async fn main() {
// connect to the database
let url = "mysql://<URL>";
let opts = Opts::from_url(url).unwrap();
let pool = Pool::new(opts).unwrap();
let mut conn = pool.get_conn().unwrap();
let mut bookresults: Vec<Bookdata> = vec![];
let _selected_results = conn
.query_map(
"SELECT id, title from books",
|(id, title)| {
bookresults.push( Bookdata { id, title } );
},
).unwrap();
for r in bookresults.iter() {
println!("id: {} - title: {}", r.id, r.title);
}
}
i had to put an underscore to silence a warning about an unused variable, so if someone knows a better way for this, im keen to learn
You should read the documentation (or at the very least, the signature) of whatever function you are trying to call. query_map() is meant to be used like you did in your first attempt, i.e., it collects the values returned by the mapped function into a Vec. However, a DB query can fail, hence it returns a Result. In your first code snippet, you were trying to iterate over the Result (which has 1 single element – the Vec of all rows – if it's Ok and 0 elements if it's Err). You should have handled the error instead in order to get the Vec out of the Result.
but since i cant get the fields from the database, i see not how i can write it to csv