get rows without duplicates

Question

I have a query I wrote a while ago that returns a count. I would now like to see the rows that are being counted but I can't seem to get my query right. Here is the query that returns the count.

extern crate rustc_serialize;

use rustc_serialize::json::{Json, ToJson};

#[derive(Debug)]
enum ApiResult<T: Sized + ToJson> {
    Ok(T),
    Err(T),
}

trait ToApiResult<T: Sized + ToJson> {
    fn to_api_result(&self) -> ApiResult<T>;
}

impl ToApiResult<Json> for Result<Option<String>, String> {
    fn to_api_result(&self) -> ApiResult<Json> {
        match *self {
            Ok(Some(ref text)) => ApiResult::Ok(text.to_json()),
            Ok(None) => ApiResult::Err(().to_json()),
            Err(ref e) => ApiResult::Err(e.to_json()),
        }
    }
}

fn main(){
    let r = Result::Ok(Some("hello".to_string()));
    print!("{:?}", r.to_api_result());
}

and here is what I have come up with, but it returns duplicate shipment numbers

    select count(distinct f_Shipmentnumber) from t_shipment shipment
    join t_Pilot pilot on pilot.f_PilotID=shipment.f_Pilot_ID
    where pilot.f_ProviderID='12' and shipment.f_ShipmentType=2 
    and shipment.f_date > DATEADD(yy, DATEDIFF(yy,0,getdate()), 0)

Any help would be great. Thank!!

Answer 1

根据你在评论中的答案，我假设当一个货物与一个货物相关联时，你不关心在结果中返回哪个飞行员。在这种情况下，您可以使用CTE和Row_Number（）函数来解决此问题：

WITH cte AS (
    select *
    , ROW_NUMBER() OVER (PARTITION BY f_Shipmentnumber ORDER BY f_Shipmentnumber) AS rn
    from t_shipment shipment
    join t_Pilot pilot on pilot.f_PilotID=shipment.f_Pilot_ID
    where pilot.f_ProviderID='12' and shipment.f_ShipmentType=2
    and shipment.f_date > DATEADD(yy, DATEDIFF(yy,0,getdate()), 0)
)
SELECT * FROM CTE WHERE rn=1

Answer 2

You have to use group by, but in group by , you have to group by all columns and you have to decide which value you want to return on the other columns. some thing like this:

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