Question

我们说我有一张带有复合主键的表：

create table FooBar (
   fooId int not null,
   barId int not null,
   status varchar(20) not null,
   lastModified datetime not null, 
   constraint PK_FooBar primary key (fooId, barId)
);

现在我有一些特定fooId的表格数据，可能是这样的：

1, 1, 'ACTIVE'
1, 2, 'INACTIVE'

...我想制作一份MERGE声明，将此表格数据视为仅fooId 1 的权威，删除FooBar中的任何不匹配记录适用于fooId 1，但保留所有<{1}}的记录不 1。

例如，我们假设fooId表目前有这些数据：

FooBar

我想用上面提到的两个数据集运行一个merge语句，1, 1, 'ACTIVE', ... (some date, not typing it out) 2, 1, 'ACTIVE', ... 1, 3, 'INACTIVE', ... 2, 2, 'INACTIVE'中的结果数据集应如下所示：

FooBar

我希望删除行1, 1, 'ACTIVE', ... 2, 1, 'ACTIVE', ... 1, 2, 'INACTIVE', ... 2, 2, 'INACTIVE', ...，并使用新修改的时间戳更新1, 3, 'INACTIVE'行，并插入1, 1, 'ACTIVE'行。我还希望1, 2, 'INACTIVE' of 2的记录不被修改。

这可以在一个声明中完成吗？如果是这样，怎么样？

Answer 1

您可以使用common table expressions作为目标和来源，在这些ctes中，您可以应用过滤器来定义您要使用的行：

-- t = Target = Destination Table = Mirror from Source
-- s = Source = New Data source to merge into Target table 

declare @FooId int = 1;

;with t as (
  select fooId, barId, [status], lastModified 
  from dbo.FooBar f 
  where f.fooId = @FooId
  )
,  s as (
  select fooId, barId, [status], lastModified=sysutcdatetime() 
  from src 
  where src.fooId = @FooId
  )
merge into t with (holdlock) -- holdlock hint for race conditions
using s 
  on (s.FooId = t.FooId and s.barId = t.barId)

    /* If the records matches, update status and lastModified. */
    when matched 
      then update set t.[status] = s.[status], t.lastModified = s.lastModified

    /* If not matched in table, insert the record */
    when not matched by target
      then insert (fooId,  barId,   [status],  lastModified)
        values (s.fooId, s.barId, s.[status], s.lastModified)

    /* If not matched by source, delete the record*/
    when not matched by source
      then delete
 output $action, inserted.*, deleted.*;

rextester演示：http://rextester.com/KRAI9699

返回：

+---------+-------+-------+----------+---------------------+-------+-------+----------+---------------------+
| $action | fooId | barId |  status  |    lastModified     | fooId | barId |  status  |    lastModified     |
+---------+-------+-------+----------+---------------------+-------+-------+----------+---------------------+
| INSERT  | 1     | 2     | INACTIVE | 2017-09-06 16:21:21 | NULL  | NULL  | NULL     | NULL                |
| UPDATE  | 1     | 1     | ACTIVE   | 2017-09-06 16:21:21 | 1     | 1     | ACTIVE   | 2017-09-06 16:21:21 |
| DELETE  | NULL  | NULL  | NULL     | NULL                | 1     | 3     | INACTIVE | 2017-09-06 16:21:21 |
+---------+-------+-------+----------+---------------------+-------+-------+----------+---------------------+

merge参考：

MERGE与DELETE在目标上与源部分匹配？

1 个答案: