-- Assuming your table is named 'vaccination_data'
-- Columns: 'Country', 'Date', 'daily_vaccinations'

-- Update missing daily_vaccinations with the median value for each country
UPDATE vaccination_data
SET daily_vaccinations = (
    SELECT COALESCE(median_daily_vaccinations, 0)
    FROM (
        SELECT 
            Country, 
            PERCENTILE_CONT(0.5) WITHIN GROUP (ORDER BY daily_vaccinations) OVER (PARTITION BY Country) AS median_daily_vaccinations
        FROM vaccination_data
        WHERE daily_vaccinations IS NOT NULL
    ) AS subquery
    WHERE subquery.Country = vaccination_data.Country
)
WHERE daily_vaccinations IS NULL;