SQL刪除重複的記錄，並留下其餘

Question

我有2個表a和b。 A有5條記錄，B有與A相同的記錄，但有7條記錄。這是7行中的相同值。我想刪除B中的前5個記錄，因爲行號與A相匹配。如何執行此操作。請幫幫我。

表：一個

col1 col2 col3 DuplicateCount 
    1  2  n   1 
    1  2  n   2 
    1  2  n   3 
    1  2  n   4 
    2  2  m   1 
    2  2  m   2 

表B：

col1 col2 col3 DuplicateCount 
    1 2  n   1 
    1 2  n   2 
    1 2  n   3 
    1 2  n   4 
    1 2  n   5 
    1 2  n   6 

期望的數據應當駐留在表B是

col1 col2 col3 DuplicateCount 

    1 2 n  5  
    1 2 n  6 

這只不過是最後2個表中的行灣

Answer 1

您可以使用TOP關鍵字刪除前五個記錄

DELETE TOP (select * from TableA a,TableB b where a.col1=b.col1 AND a.col2=b.col2 AND 
a.col3=b.col3) FROM TableA 

或

注：以下是基於它們的ID刪除一個或多個記錄的例子

DELETE From yourTable where ID in (2,3,4,5,6) 

Answer 2

試試這個：

delete from TableB 
WHERE Id IN 
(
    select b.id 
    from TableB b, TableA a 
    WHERE b.Id = a.ID 
) 

Answer 3

我添加ID列，以確定表B中的行，我不知道怎麼只有一些重複的行沒有ID列的刪除：

declare @a table 
(
    id int primary key, 
    col1 int, 
    col2 int, 
    col3 varchar 
) 

declare @b table 
(
    id int primary key, 
    col1 int, 
    col2 int, 
    col3 varchar 
) 

insert into @a values (1,1,2,'n') 
insert into @a values (2,1,2,'n') 
insert into @a values (3,1,2,'n') 
insert into @a values (4,1,2,'n') 
insert into @a values (5,2,2,'n') 
insert into @a values (6,2,2,'n') 


insert into @b values (10,1,2,'n') 
insert into @b values (20,1,2,'n') 
insert into @b values (30,1,2,'n') 
insert into @b values (40,1,2,'n') 
insert into @b values (50,1,2,'n') 
insert into @b values (60,1,2,'n') 


delete from @b 
where id in 
(
    (
     select t1.id from 
     (
      select 
       id, 
       cnt = count(*) over(partition by col1, col2, col3), 
       rn = row_number() over(partition by col1, col2, col3 order by id) 
      from @b 
     ) t1 
     join 
     (
      select 
       *, 
       cnt = count(*) over(partition by col1, col2, col3) 
      from @a 
     ) t2 on 
      t1.cnt > 1 and t1.rn <= t2.cnt 
    ) 
) 

select * from @b