我正在编写一个程序，需要从sqlite刚刚创建的最后一个插入中取回id。
db.execute("insert into short_names (short_name) values (?1)",params![short]).expect("db insert fail");
let id = db.execute("SELECT id FROM short_names WHERE short_name = '?1';",params![&short]).query(NO_PARAMS).expect("get record id fail");
let receiver = db.prepare("SELECT id FROM short_names WHERE short_name = "+short+";").expect("");
let id = receiver.query(NO_PARAMS).expect("");
println!("{:?}",id);
我应该找回的是用AUTOINCREMENT自动分配的id值sqlite。
我遇到此编译器错误：
error[E0599]: no method named `query` found for type `std::result::Result<usize, rusqlite::Error>` in the current scope
--> src/main.rs:91:100
|
91 | let id = db.execute("SELECT id FROM short_names WHERE short_name = '?1';",params![&short]).query(NO_PARAMS).expect("get record id fail");
| ^^^^^
error[E0369]: binary operation `+` cannot be applied to type `&str`
--> src/main.rs:94:83
|
94 | let receiver = db.prepare("SELECT id FROM short_names WHERE short_name = "+short+";").expect("");
| ------------------------------------------------^----- std::string::String
| | |
| | `+` cannot be used to concatenate a `&str` with a `String`
| &str
help: `to_owned()` can be used to create an owned `String` from a string reference. String concatenation appends the string on the right to the string on the left and may require reallocation. This requires ownership of the string on the left
|
94 | let receiver = db.prepare("SELECT id FROM short_names WHERE short_name = ".to_owned()+&short+";").expect("");
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ^^^^^^
error[E0277]: `rusqlite::Rows<'_>` doesn't implement `std::fmt::Debug`
--> src/main.rs:96:25
|
96 | println!("{:?}",id);
| ^^ `rusqlite::Rows<'_>` cannot be formatted using `{:?}` because it doesn't implement `std::fmt::Debug`
|
= help: the trait `std::fmt::Debug` is not implemented for `rusqlite::Rows<'_>`
= note: required by `std::fmt::Debug::fmt`
第94行：我知道rust的String不是用于execute调用的正确类型，但是我不确定该怎么做。
[我怀疑需要发生的情况是short_names表需要从数据库中拉出，然后从表的rust表示形式中获取与我要使用的id相匹配的short。 I've been going off this example as a jumping off point, but It's dereferenced it's usefulness.我正在编写的程序调用另一个程序，然后在另一个程序运行时对其进行照看。为了减少开销，我正在尝试对当前程序不使用OOP。
我应该如何构造对数据库的请求以得到所需的id？
好。首先，我们are将使用struct，因为与Java不同，它实际上等同于在这种情况下不使用一个Connection::last_insert_rowid()，除了您可以保留事物tidy 。
您正在尝试模仿Connection::last_insert_rowid()，这并不是一件非常明智的事情，特别是如果您不在交易中。我们还将以一种简洁的方式为您清除此问题：
use rusqlite::{Connection};
pub struct ShortName {
pub id: i64,
pub name: String
}
pub fn insert_shortname(db: &Connection, name: &str) -> Result<ShortName, rusqlite::Error> {
let mut rtn = ShortName {
id: 0,
name: name.to_string()
};
db.execute("insert into short_names (short_name) values (?)",&[name])?;
rtn.id = db.last_insert_rowid();
Ok(rtn)
}
您可以说服自己，它可以在此测试中使用：
#[test]
fn it_works() {
let conn = Connection::open_in_memory().expect("Could not test: DB not created");
let input:Vec<bool> = vec![];
conn.execute("CREATE TABLE short_names (id INTEGER PRIMARY KEY AUTOINCREMENT, short_name TEXT NOT NULL)", input).expect("Creation failure");
let output = insert_shortname(&conn, "Fred").expect("Insert failure");
assert_eq!(output.id, 1);
}