How to generate columns dynamically? - asp.net

Question

I have table with certain number of columns.
I want to populate other table with the data of a particular column of Table1 as columns of table2 dynamically.
When I say dynamically I mean to say that when ever any data is added to the column of Table1 the table2 is populated with as many number of columns.

Answer 1

Changing the schema on the fly really isn't a good idea, for a number of reasons. From what you've described, I think you would be better off using a view for this. A view will give you the dynamic capabilities you're looking for with fewer side effects.
See this article:
How to create a view in SQL Server

Answer 2

I will once again repeat the disclaimer that this is a bad idea, many things can go wrong, and I'm certain there is a better solution to whatever underlying problem you're trying to solve. That said, to answer the explicit question anyway, here is an example of how to do this:
USE tempdb;
GO
CREATE TABLE dbo.Table1(Description VARCHAR(32));
CREATE TABLE dbo.Table2(ID INT);
GO
CREATE TRIGGER dbo.CatchNewTable1Data
ON dbo.Table1
FOR INSERT
AS
BEGIN
SET NOCOUNT ON;
DECLARE #sql NVARCHAR(MAX) = N'';
SELECT #sql += CHAR(13) + CHAR(10) +
'ALTER TABLE dbo.Table2 ADD '
+ QUOTENAME(d) + ' VARCHAR(255);' -- guessing on destination data type
FROM
(
SELECT DISTINCT d = LEFT([Description], 128) -- identifier <= 128
FROM inserted AS i
WHERE NOT EXISTS
(
SELECT 1 FROM sys.columns
WHERE name = LEFT(i.[Description], 128)
AND [object_id] = OBJECT_ID('dbo.Table2')
)
) AS x;
EXEC sp_executesql #sql;
END
GO
Now, let's try it out! Try a column that already exists, a multi-row insert where one of the columns already exists, a multi-row insert with dupes, etc. I am not posting a value > 255 nor am I dealing with any fancy characters that will cause a problem. Why? Because ultimately I don't want you to use this solution, I want to solve the real problem. But for the googlers I want to show that there is a solution to the stated problem.
-- does nothing:
INSERT dbo.Table1 SELECT 'ID';
-- only adds column 'foo':
INSERT dbo.Table1 SELECT 'ID'
UNION ALL SELECT 'foo';
-- adds both of these columns:
INSERT dbo.Table1 SELECT 'bar'
UNION ALL SELECT 'splan foob';
-- only adds one of these:
INSERT dbo.Table1 SELECT 'blat'
UNION ALL SELECT 'blat';
SELECT * FROM dbo.Table2;
Results:
ID foo bar splan foob blat
----------- ------------ ------------ ------------ ------------
Don't forget to clean up:
DROP TABLE dbo.Table1, dbo.Table2;