Numbers table explanation

[pbsadmin]

Hi,

I'm new to T-SQL and programming in general, and had a question regarding some code used to generate a numbers table. I realize there is more than one way to do this, I am curious as to what the statement

SELECT n + @rc does. To me it appears it is simply placing the contents of the @rc variable into the single column table, but I'm not sure.

When I change the statement SET @rc = @rc * 2 to
SET @rc = @rc * 4 I get the following results

n
-----------
1
2

n
-----------
1
2
5
6

n
-----------
1
2
5
6
17
18
21
22

I'm not quite understanding why the table contains the numbers 1, 2, 3 ,4

n
-----------
1
2

n
-----------
1
2
3
4

when to me it appears like the table should contain

n
------------
1
2
4
8

etc

help would be appreciated, thanks

example with "2" below

IF OBJECT_ID('dbo.Nums', 'U') IS NOT NULL

DROP TABLE dbo.Nums;

CREATE TABLE dbo.Nums(n INT NOT NULL PRIMARY KEY);

DECLARE @max AS INT, @rc AS INT;

SET @max = 100;
SET @rc = 1;

INSERT INTO dbo.Nums(n) VALUES(1);

WHILE @rc * 2 <= @max
	
	BEGIN

		INSERT INTO dbo.Nums(n)
		SELECT n + @rc
		
		FROM dbo.Nums;                   
		
		SELECT n                       
     	        FROM dbo.Nums                 
	    
	        SET @rc = @rc * 2;                  

	END

truncated results

n
-----------
1
2

n
-----------
1
2
3
4

n
-----------
1
2
3
4
5
6
7
8

n
-----------
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16

 

[Savil]

The odd number is coming from the loop "SELECT n + @rc FROM dbo.Nums"
The first row to go into the table is a insert values of 1
When you select n from dbo.nums it will pick the first row where the value will always be one

SET @rc = 1
INSERT INTO dbo.Nums VALUES(1)
First row of the table will be 1

First pass of the loop inserts n=1 plus @rc=1
You now have 2 rows 1,2
You reset @rc to @rc * 2 (1 * 2) = 2

Next pass of the loop inserts n=1 plus @rc=2
You now have 3 rows 1,2,3

You reset @rc to @rc * 2 (2 * 2) = 4
You now have 4 rows 1,2,3,4

Change
INSERT INTO dbo.Nums SELECT n + @rc FROM dbo.Nums
to
INSERT INTO dbo.Nums SELECT MAX * 2 FROM dbo.Nums and do away the @rc variable completely