SQL Query:

WITH AllExpirationDates AS (
    -- Combine patent and exclusivity expiration dates
    SELECT
        patent_expire_date AS expiration_date
    FROM
        orange_book_patents
    WHERE
        patent_expire_date IS NOT NULL

    UNION ALL

    SELECT
        exclusivity_date AS expiration_date
    FROM
        orange_book_exclusivities
    WHERE
        exclusivity_date IS NOT NULL
),
FilteredExpirations AS (
    -- Filter for expiration dates within the current year
    SELECT
        expiration_date
    FROM
        AllExpirationDates
    WHERE
        EXTRACT(YEAR FROM expiration_date) = EXTRACT(YEAR FROM CURRENT_DATE)
),
MonthlyCounts AS (
    -- Count expirations per month for the current year
    SELECT
        EXTRACT(MONTH FROM expiration_date)::integer AS month_num,
        COUNT(*) AS expiration_count
    FROM
        FilteredExpirations
    GROUP BY
        1
),
CalendarMonths AS (
    -- Generate all month numbers and YYYY-MM format for the current year
    SELECT
        EXTRACT(MONTH FROM gs)::integer AS month_num,
        TO_CHAR(gs, 'YYYY-MM') AS month_year
    FROM
        GENERATE_SERIES(
            date_trunc('year', CURRENT_DATE),
            date_trunc('year', CURRENT_DATE) + interval '11 months',
            '1 month'
        ) AS gs
)
-- Select the month and the count, including months with zero expirations
SELECT
    cm.month_year,
    COALESCE(mc.expiration_count, 0) AS total_expirations
FROM
    CalendarMonths cm
LEFT JOIN
    MonthlyCounts mc ON cm.month_num = mc.month_num
ORDER BY
    cm.month_num
LIMIT 20;