HA - SQL - Get eletricity consumption from statistics table

/*******************************************************************************
Extract current month total electricity consumption from long term statistics
table in Home Assistant and calculate average price per kWh
*******************************************************************************/
SELECT
    price,
    kwh,
    price/kwh as avg_rate
FROM
    (
    SELECT
        end_kwh - start_kwh as kwh,
        end_price - start_price as price
    FROM
        (
        SELECT
            (SELECT state FROM `statistics` s left JOIN `statistics_meta` m on s.metadata_id=m.id WHERE m.statistic_id='sensor.kamstrup_total_import_filter' AND EXTRACT(YEAR_MONTH FROM start) < EXTRACT(YEAR_MONTH FROM CURRENT_DATE)  ORDER BY start DESC LIMIT 1) As start_kwh,
            (SELECT state FROM `statistics` s left JOIN `statistics_meta` m on s.metadata_id=m.id WHERE m.statistic_id='sensor.kamstrup_total_import_filter' AND EXTRACT(YEAR_MONTH FROM start) = EXTRACT(YEAR_MONTH FROM CURRENT_DATE)  ORDER BY start DESC LIMIT 1) As end_kwh,
            (SELECT sum FROM `statistics` s left JOIN `statistics_meta` m on s.metadata_id=m.id WHERE m.statistic_id='sensor.kamstrup_total_import_filter_cost' AND EXTRACT(YEAR_MONTH FROM start) < EXTRACT(YEAR_MONTH FROM CURRENT_DATE)  ORDER BY start DESC LIMIT 1) As start_price,
            (SELECT sum FROM `statistics` s left JOIN `statistics_meta` m on s.metadata_id=m.id WHERE m.statistic_id='sensor.kamstrup_total_import_filter_cost' AND EXTRACT(YEAR_MONTH FROM start) = EXTRACT(YEAR_MONTH FROM CURRENT_DATE)  ORDER BY start DESC LIMIT 1) As end_price
        ) As data
    ) As data2;