在SQL Server中删除重复项并保留一个条件

Question

我正在使用SQL Server。

我有以下设计的表：

ID bigint 
Number varchar(50) 
Processed int 

我有很多重复的数列

我要删除所有重复的数字，并保持数where processed=1

举例如果我有

Number --- Processed 
111 --- 0 
111 --- 0 
111 --- 1 

I要删除所有，并保持最后一个

任何帮助，将不胜感激

Answer 1

如果你只是想删除其中数等于111行和处理不等于1，你可以这样做：

delete from <table> 
where 
Number = 111 and 
Processed <> 1 

假设ID是连续的，你想保留的最后一排的每个号码，你可以这样做：

delete from <table> t 
left join (
    select 
     MAX(ID) filter_ID 
    from <table> 
    group by 
     Number 
) filter on 
    t.ID = filter.filter_ID 
where 
    filter.filter_ID is null 

让每个号码优先至少一行到加工= 1

delete from <table> t 
left join (
    select 
    ID 
    from (
     select 
      ROW_NUMBER() OVER (
       PARTITION BY 
        Number 
       ORDER BY 
        Processed DESC, 
        ID DESC 
      ) last_R, 
      ID 
     from <table> 
    ) filter 
    where 
     last_R = 1 
) filter on 
    t.ID = filter.filter_ID 
where 
    filter.filter_ID is null 

Answer 2

这是我会怎么处理这个问题：

DECLARE @NUM VARCHAR(50) 
DECLARE @TAB TABLE 
(
    NUMBER VARCHAR(50) 
) 

INSERT INTO @TAB 
SELECT number, from <table> where processed = 0 GROUP BY number HAVING COUNT(number) > 1 

DECLARE @IDToKEEP TABLE 
(
    id INT 
) 

WHILE (SELECT COUNT(*) FROM @TAB) > 0 
BEGIN 
    SELECT TOP 1 @NUM = number FROM @TAB 

    INSERT INTO @IDToKEEP 
    SELECT TOP 1 id FROM <table> WHERE number = @NUM 

    DELETE FROM @TAB WHERE number = @NUM 
END 

DELETE FROM <table> WHERE processed = 0 AND number IN (SELECT number FROM @TAB) AND id NOT IN (SELECT id FROM @IDToKEEP) 

Answer 3

这里有一个方法：

with todelete as (
     select t.*, 
      row_number() over (partition by number order by processed desc) as seqnum 
     from table t 
    ) 
delete from todelete 
    where seqnum > 1; 

的row_number()枚举行，使用处理作为优先级。该逻辑可确保只剩一行，即使没有任何行有processed = 1。