Insert two columns from different tables - sql-server

Question

I need to write an insert query to insert some rows into a table using data from different tables. I have:
A variable #ID which contains ID of the new inserted row in a table. (1)
A table (2) contains some IDs
A table (3) define the relation between the two above tables.
Now I need to insert for each ID in (2) a new row in the table (3).
So if #ID=2 and IDs = 1, 2, 3, 4, 5, 6, I want to insert the following rows in Table (3):
table1_ID table2_ID
--------- ---------
1 1
1 2
1 3
1 4
1 5

Answer 1

Assuming that the value 6 was not meant to be discarded (if it was, please explain the logic). Also assuming that you just want every row in table 2 inserted into table 2.
INSERT dbo.Table3(table1_ID, table2_ID)
SELECT #ID, ID
FROM dbo.Table2
-- WHERE ID <> 6???
;
If the list of IDs is really a CSV, then:
First create a Split function (several alternatives described here, except they output strings instead of integers), e.g.
CREATE FUNCTION dbo.SplitInts
(
#List VARCHAR(MAX),
#Delimiter VARCHAR(255)
)
RETURNS #t TABLE(Item INT)
AS
BEGIN
INSERT #t(Item) SELECT CONVERT(INT, SUBSTRING(#List, Number,
CHARINDEX(#Delimiter, #List + #Delimiter, Number) - Number))
FROM (SELECT ROW_NUMBER() OVER (ORDER BY [object_id])
FROM sys.all_objects) AS n(Number)
WHERE Number <= CONVERT(INT, LEN(#List))
AND SUBSTRING(#Delimiter + #List, Number, 1) = #Delimiter;
RETURN;
END
GO
Now your stored procedure can simply say:
CREATE PROCEDURE dbo.whatever
#ID INT,
#IDs VARCHAR(MAX)
AS
BEGIN
SET NOCOUNT ON;
INSERT dbo.Table3(table1_ID, table2_ID)
SELECT #ID, Item
FROM dbo.SplitInts(#IDs, ',');
END
GO
However if you are on SQL Server 2008 or above, and this list of comma-separated IDs is coming from your application (e.g. from a DataTable or other set), you could use a Table-Valued Parameter and avoid the need for splitting.
CREATE TYPE dbo.SetOfIntegers
( Number INT );
GO
CREATE PROCEDURE dbo.whatever
#ID INT,
#IDs dbo.SetOfIntegers READONLY
AS
BEGIN
SET NOCOUNT ON;
INSERT dbo.Table3(table1_ID, table2_ID)
SELECT #ID, Item
FROM #IDs;
END
GO
Then you have to change the C# code to pass your DataTable in as SqlDbType.Structured instead of passing your CSV in as a string. More info here:
http://www.sqlperformance.com/2012/08/t-sql-queries/splitting-strings-now-with-less-t-sql