select block_number as first_block_number, block_timestamp

from polygon.core.fact_transactions

),

base1 as (

select first_block_number + 1 as second_block_number, block_timestamp

from base

),

info as (

select ft.block_number as bn, timestampdiff('SECOND', base1.BLOCK_TIMESTAMP, base.block_timestamp) AS time_diff

from polygon.core.fact_transactions ft

inner join base on base.first_block_number = ft.block_number

inner join base1 on base1.second_block_number = ft.block_number)

select sum(time_diff)/count(bn) as average_block_time

from info