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

问题

I know that when I insert a row into a table with an identity column, I can retrieve the ID of the row I just inserted using SELECT @@IDENTITY.

If I do an insert statement that inserts ten rows into that same table, is there a practical way to get the IDs of all ten rows?

回答1:

Yes, use the OUTPUT clause. You should be using that as a first choice anyway.

Even better you can return more than one field with OUTPUT. SO you can popuate a table variable with the surrogate key and the natural key.

回答2:

The OUTPUT clause with INSERT has a lack: it is impossible to say after insert which Id was assigned for each row in source table.

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;

In the example above we will get the list of actual Ids in @Persistent table, but we can not map those Ids to Ids in @Temporary table, because OUPTUT in INSERT does not allow to get source table fields - it gets only INSERTED table fields.

As opposed to INSERT, the OUPTUT clause in MERGE allows to get fields from a source table. So using the OUTPUT with MERGE solves the problem:

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;

Below is the example of using the MERGE command to insert-update-delete rows in parent-child tables. The collection of target-source-mapping from MERGE OUTPUT is very usefull:

-- 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;

来源：https://stackoverflow.com/questions/28375683/does-sql-server-have-something-like-identity-that-returns-multiple-values

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sql-server

tsql