SQL 服务器是否有类似 @@IDENTITY 的东西 returns 多个值？

Question

我知道当我将一行插入带有标识列的 table 时，我可以使用 SELECT @@IDENTITY.

检索我刚刚插入的行的 ID

如果我执行插入语句将十行插入同一个 table，是否有实用的方法来获取所有十行的 ID？

Answer 1

是的，使用 OUTPUT 子句。无论如何，您应该将其作为首选。

更好的是，您可以 return 多个带有 OUTPUT 的字段。因此，您可以使用代理键和自然键填充 table 变量。

Answer 2

带有 INSERT 的 OUTPUT 子句有一个缺陷：在插入之后不可能说出源 table 中的每一行分配了哪个 ID。

declare @Persistent table (Id int not null identity primary key, Value varchar(10));
declare @Temporary table (Id int not null primary key, Value varchar(10));

insert into @Temporary values (11, 'AAA'), (22, 'AAA'), (33, 'CCC');

insert into @Persistent (Value)
output inserted.Id
select Value from @Temporary;

在上面的示例中，我们将在@Persistent table 中获取实际 ID 列表，但我们无法将这些 ID 映射到 @Temporary table 中的 ID，因为 INSERT 中的 OUPTUT 不会允许获取源 table 字段 - 它只获取 INSERTED table 字段。

与 INSERT 不同，MERGE 中的 OUPTUT 子句允许从源 table 获取字段。所以使用 MERGE 的 OUTPUT 解决了问题：

merge into @Persistent as target
    using @Temporary as source on source.Id = target.Id        
when matched then
    update set Value = source.Value    
when not matched then
    insert (Value) values (Value)    
output 
    inserted.Id, source.Id;

下面是使用 MERGE 命令在父子 table 中插入-更新-删除行的示例。从 MERGE OUTPUT 收集的 target-source-mapping 非常有用：

-- definition of persistent tables

declare @Parents table (Id int not null identity primary key, Name varchar(10));
declare @Children table (Id int not null identity primary key, ParentId int, Name varchar(10));

-- imagine that persistent tables contain some data

insert into @Parents (Name) select 'Alfa';
insert into @Children (ParentId, Name) select 1, 'Delta';

-- definition of temporary tables

declare @TempParents table (Id int not null primary key, Name varchar(10));
declare @TempChildren table (Id int not null primary key, ParentId int, Name varchar(10));

-- data to insert (with negative Ids) and update (with real positive Ids)

insert into @TempParents values 
   (1, 'Alpha'), (-2, 'Bravo'), (-1, 'Charlie');

insert into @TempChildren values 
   (-9, 1, 'Alpha-1'),   (-8, 1, 'Alpha-2'),   (-7, 1, 'Alpha-2'),
   (-6, -2, 'Bravo-1'),   (-5, -2, 'Bravo-2'),   (-4, -2, 'Bravo-3'),
   (-3, -1, 'Charlie-1'), (-2, -1, 'Charlie-2'), (-1, -1, 'Charlie-3');

-- table to collect mapping Ids from @TempParents to @Parents

declare @ParentIdMaps table (ParentId int, TempParentId int)

-- merge data into @Parents table and collection of mapping Ids

merge into @Parents as target
using @TempParents as source on source.Id = target.Id    
when matched then
   update set   Name = source.Name
when not matched then
   insert (Name) values (Name)
output 
   inserted.Id, source.Id
into @ParentIdMaps
   (ParentId, TempParentId);

-- merge data into @Children table and use of mapping Ids

merge into @Children as target
using 
    (
       select
          Id,
          ParentId = m.ParentId,
          Name
       from
          @TempChildren tc
          inner join @ParentIdMaps m on m.TempParentId = tc.ParentId    
    )  
    as source on source.Id = target.Id    
when matched then
   update set ParentId = source.ParentId, Name = source.Name
when not matched then
   insert (ParentId, Name) values (ParentId, Name)
when not matched by source and target.ParentId in (select Id from @TempParents) then
   delete;

-- checking the result
-- see that 'Alfa' was renamed to 'Alpha' 
-- and 'Delta' was deleted because it was not mentioned in @TempChildren

select 
   p.*, 
   c.*
from      
   @Parents p
   inner join @Children c on c.ParentId = p.Id
order by
   p.Id,
   c.Id;

SQL 服务器是否有类似 @@IDENTITY 的东西 returns 多个值？

Does SQL Server have something like @@IDENTITY that returns multiple values?

tsql

sql-server