SQL Running Total and Window Function Query Generator for ERP Tables

SELECT
    item_code,
    transaction_date,
    transaction_id,
    quantity_signed,
    SUM(quantity_signed) OVER (
        PARTITION BY item_code
        ORDER BY transaction_date, transaction_id
        ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW
    ) AS running_total
FROM dbo.inventory_transactions
WHERE warehouse = 'MAIN'
ORDER BY item_code, transaction_date, transaction_id;

SELECT
    item_code,
    transaction_date,
    quantity_signed,
    LAG(quantity_signed) OVER (
        PARTITION BY item_code
        ORDER BY transaction_date, transaction_id
    ) AS previous_value,
    quantity_signed - LAG(quantity_signed, 1, 0) OVER (
        PARTITION BY item_code
        ORDER BY transaction_date, transaction_id
    ) AS change_from_previous
FROM dbo.inventory_transactions
WHERE warehouse = 'MAIN';

WITH ranked AS (
    SELECT
        t.*,
        ROW_NUMBER() OVER (
            PARTITION BY item_code
            ORDER BY transaction_date DESC, transaction_id DESC
        ) AS rn
    FROM dbo.inventory_transactions AS t
    WHERE warehouse = 'MAIN'
)
SELECT *
FROM ranked
WHERE rn <= 3
ORDER BY item_code, rn;

SELECT
    item_code,
    transaction_date,
    quantity_signed,
    SUM(quantity_signed) OVER (PARTITION BY item_code) AS group_total,
    CASE WHEN SUM(quantity_signed) OVER (PARTITION BY item_code) = 0
         THEN 0
         ELSE 100.0 * quantity_signed / SUM(quantity_signed) OVER (PARTITION BY item_code)
    END AS pct_of_group
FROM dbo.inventory_transactions
WHERE warehouse = 'MAIN';