Loop a result set and feed two tables - tsql

Question

I have a select query that returns a huge result set (500k records). But for this example let's say it has only two records:
SELECT * FROM INVENTORY I
INNER JOIN PARTS P
ON I.partcode = P.partcode
ORDER BY I.partcode
The result will look more or less like this:
pk partcode genericname partname stock
1 001 mouse logitech 10
2 002 keyboard genius 8
I have to loop the result above and feed two tables (product and variant).
I first have to insert two of the columns into 'product' table, like this:
INSERT INTO PRODUCT
(p_code,product_name) values (partcode,genericname)
pk p_code product_name
5 001 mouse
6 001 keyboard
Then I have to grab the pk that was automatically generated into the table above (say ppk) and then insert it together with the other two columns into the 'variant' table, like this:
INSERT INTO VARIANT
(product_pk,variant_name,in_stock) values (ppk,partname,stock)
pk product_pk variant_name in_stock
10 5 logitech 10
11 6 genius 8
At the end I should have the product and the variant tables with 2 records each.
I could write a VB code to do that but I think that it can de done in pure SQL, and I just am not sure the best approach.
Someone could give me some help with this?
Thank you!

Answer 1

You could use a SQL cursor to loop through and insert a row at a time into PRODUCT and then use SCOPE_IDENTITY() to get the newly assigned identity value to insert a corresponding row into VARIANT, but best practice is to avoid cursors if there's another way. (There usually is, but not always.)
If the partcode/genericname combination will uniquely identify 1 record in PRODUCT, you could do this:
INSERT INTO PRODUCT (p_code,product_name)
SELECT partcode, genenricname
FROM INVENTORY I INNER JOIN PARTS P ON I.partcode = P.partcode
(I would eliminate the ORDER BY from your query unless you care about the order the identity values are assigned.)
Then, run this:
INSERT INTO VARIANT
(product_pk,variant_name,in_stock)
SELECT pr.ppk, i.partname, i.stock
FROM inventory i INNER JOIN parts p ON i.partcode = p.partcode
INNER JOIN product pr on i.partcode = pr.p_code and i.genericname = pr.product_name
You may have to clean up the aliases between i and p in the 2nd query. I can't tell which table (inventory or parts) the variant_name and in_stock fields are coming from so I just used i.
Again - this assumes that partcode/genericname combination is unique in the PRODUCT table.