Do Inserted Records Always Receive Contiguous Identity Values

Question

Consider the following SQL:

CREATE TABLE Foo
(
    ID int IDENTITY(1,1),
    Data nvarchar(max)
)

INSERT INTO Foo (Data)
SELECT TOP 1000 Data
FROM SomeOther         


        

Answer 1

Yes, they will be contiguous because the INSERT is atomic: complete success or full rollback. It is also performed as a single unit of work: you wont get any "interleaving" with other processes

However (or to put your mind at rest!), consider the OUTPUT clause

DECLARE @KeyStore TABLE (ID int NOT NULL)

INSERT INTO Foo (Data)
OUTPUT INSERTED.ID INTO @KeyStore (ID) --this line
SELECT TOP 1000 Data
FROM SomeOtherTable
WHERE SomeColumn = @SomeParameter