Write a PL/pgSQL block to find out count of completed month between two dates enter by the user.

Sure, here is a PL/pgSQL block that calculates the count of completed months between two dates entered by the user:

DO $$
DECLARE
    start_date DATE;
    end_date DATE;
    month_count INT;
BEGIN
    -- Replace '2022-01-01' and '2022-12-31' with the dates entered by the user
    start_date := '2022-01-01';
    end_date := '2022-12-31';

    month_count := (EXTRACT(YEAR FROM end_date) - EXTRACT(YEAR FROM start_date)) * 12 + (EXTRACT(MONTH FROM end_date) - EXTRACT(MONTH FROM start_date));

    -- If the end date is earlier in the month than the start date, subtract one month
    IF EXTRACT(DAY FROM end_date) < EXTRACT(DAY FROM start_date) THEN
        month_count := month_count - 1;
    END IF;

    RAISE NOTICE 'The count of completed months is %', month_count;
END $$;

This block first calculates the difference in years and months separately, then combines them to get the total difference in months. If the day of the end date is earlier in the month than the day of the start date, it subtracts one month from the total, because that month is not completed. Finally, it outputs the result using RAISE NOTICE.

Please replace '2022-01-01' and '2022-12-31' with the dates entered by the user.