PIVOT other items in SQL - sql

Question

I have a table that I need to PIVOT its columns but I'm not sure if there's an easy way to do it.
Here's the portion of my table:
Category | Item | Total
Food | 1 | $500
Food | 2 | $1,000
Food | 3 | $750
Pivot result (which is correct):
Category | item_1 | item_2 | item_3
Food | $500 | $1,000 | $750
my code:
SELECT category,
[1] as item_1,
[2] as item_2,
[3] as item_3
FROM (
SELECT category, item, SUM(item_total) as item_total FROM (
SELECT category, item, total
FROM tbl_product
where category = 'Food'
) prod
GROUP BY category, item) sourcetable
PIVOT
(
AVG(item_total)
FOR item IN ([1],[2],[3])
) as PivotTable;
However, I do have more than 50 items. I would like to group these items into columns.
Example: items 7-20 should be in misc_1 column, 21-50 as misc_2 column
so it would look like this:
Category | item_1 | item_2 | item_3 | misc_1 | misc_2
Food | $500 | $1,000 | $750 | $8,000 | $5,700
As much as possible, I don't like to put every single items in the "item IN ([1],...)"
Please let me know if it's possible to combine those group items into single column.
Thank you.

Answer 1

You have to do the same query but dynamically, something like this:
DECLARE #cols AS NVARCHAR(MAX);
DECLARE #colnames AS NVARCHAR(MAX);
DECLARE #query AS NVARCHAR(MAX);
SELECT #cols = STUFF((SELECT distinct ',' +
QUOTENAME(item)
FROM tbl_product AS t
FOR XML PATH(''), TYPE
).value('.', 'NVARCHAR(MAX)')
, 1, 1, '');
SELECT #colnames = STUFF((SELECT distinct ',' +
QUOTENAME(item) + 'AS' +
CASE WHEN rn < 7 THEN QUOTENAME('Item_' + CAST(item AS NVARCHAR(5)))
ELSE QUOTENAME('Misc_' + CAST(item AS NVARCHAR(5))) END
FROM (SELECT ROW_NUMBER() OVER(ORDER BY item) AS rn, item FROM tbl_product) AS t
FOR XML PATH(''), TYPE
).value('.', 'NVARCHAR(MAX)')
, 1, 1, '');
SELECT #query = 'SELECT category, '+ #colnames + '
FROM (
SELECT category, item, SUM(total) as item_total
FROM (
SELECT category, item, total
FROM tbl_product
) prod
GROUP BY category, item) sourcetable
PIVOT
(
AVG(item_total)
FOR item IN (' + #cols + ')' +
') p';
execute(#query);
Note that:
For the column names, I used:
SELECT #colnames = STUFF((SELECT distinct ',' +
QUOTENAME(item) + 'AS' +
CASE WHEN rn < 7 THEN QUOTENAME('Item_' + CAST(item AS NVARCHAR(5)))
ELSE QUOTENAME('Misc_' + CAST(item AS NVARCHAR(5))) END
FROM (SELECT ROW_NUMBER() OVER(ORDER BY item) AS rn, item FROM tbl_product) AS t
FOR XML PATH(''), TYPE
).value('.', 'NVARCHAR(MAX)')
, 1, 1, '');
To select those the first 7 items with the names item_, whereas the rest of the items with the names Misc_. You can edit in this statement to customize how you would like to display the items' names.