SQL Query Duplicate Removal Help

问题

I need to remove semi duplicate records from the following table

ID      PID      SCORE
1       1        50
2       33       20
3       1        90
4       5        55
5       7        11
6       22       34

For any duplicate PID's that exist I want to remove the lowest scoring record. In the example above ID 1 would be remove. I'm trying to come up with a way of doing this without using loops but am really struggling.

Any help would be appreciated.

Thanks

回答1:

    DELETE t.* 
    FROM Table1 t 
    JOIN (SELECT pid, MIN(score) minScore, MAX(id) maxId
            FROM Table1
        GROUP BY pid) t1 
    ON t.pid = t1.pid 
   AND t.score = t1.minScore 
   AND t.id < t1.maxId

回答2:

WITH    q AS
        (
        SELECT  *, ROW_NUMBER() OVER (PARTITION BY pid ORDER BY score) AS rn
        FROM    mytable
        )
DELETE
FROM    q
WHERE   rn = 1

To leave the results that have no duplicates:

WITH    q AS
        (
        SELECT  *,
                ROW_NUMBER() OVER (PARTITION BY pid ORDER BY score) AS rn,
                COUNT(*) OVER (PARTITION BY pid) AS cnt
        FROM    mytable
        )
DELETE
FROM    q
WHERE   rn = 1
        AND cnt > 1

回答3:

try this..

    declare @tt table(id int, pid int,score int)
    insert into @tt
    select 1,1,50 union all
    select 2,33,50 union all
    select 8,33,80 union all
    select 3,1,90 union all
    select 4,5,50 union all
    select 5,5,10 union all
    select 6,6,10 union all
    select 7,6,50  
    ---------   
    delete from @tt where id in (
    select t1.id from @tt t1 inner join
    (
        select  MIN(score) tScore,pid tPid from @tt where pid in 
        (select  pid from @tt group by pid having count (pid) > 1) group by pid 
    ) t2 on t1.pid=t2.tPid and t1.score=t2.tScore)

    select * from @tt

回答4:

I can't see your query, so I've made up this example...

SELECT
    PID,
    MAX(Score)
FROM
    tblTable
GROUP BY
    PID

来源：https://stackoverflow.com/questions/1554060/sql-query-duplicate-removal-help

标签

sql

sql-server

duplicate-removal