MERGE 与 DELETE 在目标上与源上的部分匹配？

Question

假设我有一个带有复合主键的 table：

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'

...并且我想创建一个 MERGE 语句，将此表格数据视为权威 for fooId 1 only，删除 FooBar 用于 fooId 1，但保留所有带有 fooId 的记录，即 而不是 1。

例如，假设 FooBar table 当前有此数据：

1, 1, 'ACTIVE', ... (some date, not typing it out)
2, 1, 'ACTIVE', ...
1, 3, 'INACTIVE', ...
2, 2, 'INACTIVE'

我想运行合并语句与上面提到的两个数据集，FooBar 中的结果数据集应该如下所示：

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

我希望删除 1, 3, 'INACTIVE' 行，使用新修改的时间戳更新 1, 1, 'ACTIVE' 行，并插入 1, 2, 'INACTIVE' 行。我还希望 fooId of 2 的记录保持不变。

这可以在一条语句中完成吗？如果是，怎么做？

Answer 1

您可以使用 common table expressions 作为您的目标和来源，并且在这些 ctes 中您可以应用过滤器来定义您想要使用的行：

-- 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

returns:

+---------+-------+-------+----------+---------------------+-------+-------+----------+---------------------+
| $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 在目标上与源上的部分匹配？

MERGE with DELETE on target with partial match on source?

sql-server

merge

upsert