Insert numbers in table in sequence but without IDENTITY set - sql-server

Question

I have few tables, in one of them I am doing load from excel file and then i am doing insert from select
In target table i have column id which doesn't have IDENTITY on it and i cannot create it, so I used ROW_NUMBER() in my select for INSERT,
however now I am having problem, when next time I'm doing load from file into my temp table from which I am selection data for INSERT row number starts from 1 and if iam trying to do insert i am getting error obout problems with Primary key/ So i need to add ID based on id which is already in target table
for example if in target table last record 1000
first record from new Insert has to have id 1001
INSERT INTO table1
( Id ,
OkeiId ,
OkpdId ,
OkvedId ,
)
SELECT
-- (SELECT MAX (id) FROM table1) AS 'last id in table',
ROW_NUMBER() OVER ( ORDER BY ( SELECT 0 ) ) AS Row , -- Id - int
a.[Id] AS OkeId , - int
c.[Id] AS OkpId , - int
D.[Id] AS OkvId , - int
FROM [dbo].#table b
LEFT OUTER JOIN table2 a ON b.F6 = a.[NationalSymbol]
LEFT OUTER JOIN table3 c ON b.F4 = c.Code
LEFT OUTER JOIN table4 D ON b.F5 = D.Code
LEFT OUTER JOIN table1 f ON b.f1 = f.Code
WHERE f.code IS NULL
any Ideas how to continue insert id in sequence? I CANNOT use IDENTITY on this table. I hope you can understand my explanetions

Answer 1

INSERT INTO table1
( Id ,
OkeiId ,
OkpdId ,
OkvedId
)
SELECT
-- (SELECT MAX (id) FROM table1) AS 'last id in table',
a.last_id + ROW_NUMBER() OVER ( ORDER BY ( SELECT 0 ) ) AS Row , -- Id - int
a.[Id] AS OkeiId , -- OkeiId - int
c.[Id] AS OkpdId , -- OkpdId - int
D.[Id] AS OkvedId -- OkvedId - int
FROM [dbo].#table b
LEFT OUTER JOIN table2 a ON b.F6 = a.[NationalSymbol]
LEFT OUTER JOIN table3 c ON b.F4 = c.Code
LEFT OUTER JOIN table4 D ON b.F5 = D.Code
LEFT OUTER JOIN table1 f ON b.f1 = f.Code
CROSS JOIN (SELECT MAX (id) AS last_id FROM table1 ) a
WHERE f.code IS NULL
and some tests:
CREATE TABLE #a
(
a INT PRIMARY KEY,
aa int
)
CREATE TABLE #b
(
b int
)
INSERT INTO #a VALUES(1,1);
INSERT INTO #b VALUES(1);
INSERT INTO #b VALUES(2);
INSERT INTO #b VALUES(3);
INSERT INTO #b VALUES(4);
INSERT INTO #b VALUES(5);
INSERT INTO #a
SELECT last_id + ROW_NUMBER() OVER(ORDER BY b.b), b.b FROM #b b CROSS JOIN (SELECT MAX(a) last_id FROM #a) a

Answer 2

If you're unable to use IDENTITY for some reason and are on SQL Server 2012+, consider sequence numbers. They can be used with multiple columns/tables and are generally more flexible than IDENTITY. See below for examples of creation and use.
Sequence create
CREATE SEQUENCE TestSequence
AS INTEGER
START WITH 1
INCREMENT BY 1;
Sequence use
CREATE TABLE TestTable
(
TestId INTEGER NOT NULL,
TestColumn CHAR(1) NULL
);
INSERT INTO TestTable (TestId, TestColumn)
VALUES (NEXT VALUE FOR TestSequence, 'A');
SQL Fiddle