SQL with numbers - sql

Question

I am trying to build a loop with SQL Server.
When I execute SELECT 1 UNION SELECT 2 UNION SELECT 3; SQL Server creates a table with 1 column and 4 rows.
Can anyone think of a way to achive the same however without using UNION?

Answer 1

You can use the values() table constructor:
select *
from (values (1), (2), (3), (4)) v(n);

Answer 2

You can do this easily with a recursive cte.
declare #max int=4
;with cte as
(
select 1 as val
union all
select val+1
from cte
where val < #max
)
select *
from cte

Answer 3

Here's a few common options to do this in case your use case expands hundreds or thousands of rows...
Commonly seen a a tally table...
WITH
E1(N) AS (select 1 from (values (1),(1),(1),(1),(1),(1),(1),(1),(1),(1))dt(n)),
E2(N) AS (SELECT 1 FROM E1 a, E1 b), --10E+2 or 100 rows
E4(N) AS (SELECT 1 FROM E2 a, E2 b), --10E+4 or 10,000 rows max
cteTally(N) AS
(
SELECT ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) FROM E4
)
select N from cteTally
Or, using a function from Jeff Moden
CREATE FUNCTION [dbo].[fnTallyProg]
/**********************************************************************************************************************
Purpose:
Given a start value, end value, and increment, create a sequencial list of integers.
Programmers Notes:
1. The increment can be negative if the start value is greater than the end value. In other words, it can count down
as well as up.
Revison History:
Rev 00 - 18 Feb 2017 - Jeff Moden
- Rewrite original to take start, end, and increment parameters.
**********************************************************************************************************************/
(
#pStart BIGINT
,#pEnd BIGINT
,#pIncrement BIGINT
)
RETURNS TABLE WITH SCHEMABINDING AS
RETURN WITH
E01(N) AS (SELECT NULL FROM (VALUES (NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL))E0(N)) --10 rows
,E04(N) AS (SELECT NULL FROM E01 a CROSS JOIN E01 b CROSS JOIN E01 c CROSS JOIN E01 d) --10 Thousand rows
,E16(N) AS (SELECT NULL FROM E04 a CROSS JOIN E04 b CROSS JOIN E04 c CROSS JOIN E04 d) --10 Quadrillion rows, which is crazy
,Tally(N) AS (SELECT TOP (ABS((#pEnd-#pStart+#pIncrement)/#pIncrement))
N = ROW_NUMBER() OVER (ORDER BY (SELECT NULL))
FROM E16
WHERE (#pStart<=#pEnd AND #pIncrement > 0)
OR (#pStart>=#pEnd AND #pIncrement < 0)
ORDER BY N
)
SELECT TOP (ABS((#pEnd-#pStart+#pIncrement)/#pIncrement))
N = (t.N-1)*#pIncrement+#pStart
FROM Tally t
ORDER BY t.N
;
GO
Or, another quick function by JL
CREATE FUNCTION [dbo].[tfn_Tally]
(
#NumOfRows BIGINT = 1000000
,#StartWith BIGINT = 1563984
)
/* ============================================================================
07/20/2017 JL, Created. Capable of creating a sequense of rows
ranging from -10,000,000,000,000,000 to 10,000,000,000,000,000
============================================================================ */
RETURNS TABLE WITH SCHEMABINDING AS
RETURN
WITH
cte_n1 (n) AS (SELECT 1 FROM (VALUES (1),(1),(1),(1),(1),(1),(1),(1),(1),(1)) n (n)), -- 10 rows
cte_n2 (n) AS (SELECT 1 FROM cte_n1 a CROSS JOIN cte_n1 b), -- 100 rows
cte_n3 (n) AS (SELECT 1 FROM cte_n2 a CROSS JOIN cte_n2 b), -- 10,000 rows
cte_n4 (n) AS (SELECT 1 FROM cte_n3 a CROSS JOIN cte_n3 b), -- 100,000,000 rows
cte_Tally (n) AS (
SELECT TOP (#NumOfRows)
(ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) - 1) + #StartWith
FROM
cte_n4 a CROSS JOIN cte_n4 b -- 10,000,000,000,000,000 rows
)
SELECT
t.n
FROM
cte_Tally t;

Answer 4

Just for fun, you can use an ad-hoc tally table
Example
Declare #N int =4
Select Top (#N) N=Row_Number() Over (Order By (Select NULL))
From master..spt_values n1
Returns
N
1
2
3
4

Answer 5

If all you need is a sequence of values to be joined to another table later on, I would strongly suggest to create a one time auxiliary table of numbers as described here
The code to generate such table is pretty basic:
SELECT TOP (1000000) n = CONVERT(INT, ROW_NUMBER() OVER (ORDER BY s1.[object_id]))
INTO dbo.Numbers
FROM sys.all_objects AS s1 CROSS JOIN sys.all_objects AS s2
OPTION (MAXDOP 1);
CREATE UNIQUE CLUSTERED INDEX n ON dbo.Numbers(n)
That will created a persisted "Numbers" table in your db that then you can use to join to other tables or use from functions.