Question

SELECT
    *
FROM
    Registrations AS R1 
    INNER JOIN Registrations AS R2 
        ON R2.UserItemId = R1.UserItemId 
        AND R2.CourseOfferingId = R1.CourseOfferingId 
        AND R2.Id != R1.Id
WHERE
    R2.Id > R1.Id

我应该如何删除重复的值？

由于

Answer 1

您可以尝试这样的查询

;with cte as (
select *, RowN = row_number() over(partition by useritemid, courseofferingid, id order by id) from Registrations )
delete from cte where Rown > 1

Answer 2

我会抓住你的问题。根据您提供的查询，这只是猜测。一个完整的问题将描述重复行的确切含义。

delete from Registrations
where exists (
    select 1
    from Registrations r2
    where   r2.UserItemId = Registrations.UserItemId
        and r2.CourseOfferingId = Registrations.CourseOfferingId
        and r2.Id < Registrations.Id
);

显然，您有多个行具有相同的UserItemId和CourseOffereningId但不同的Id值。我假设您要保留最低Id的那个并丢弃其他人。

查询中的子查询占用表中的每一行，并检查是否有另一行像这样但具有较低的Id。如果答案是肯定的话则删除该行。

在SQL中删除重复值

2 个答案: