Voeg 2 tabellen samen waar twee reeksen getallen elkaar overlappen binnen de samenvoegkolommen

Het idee is om eerst een lijst met unieke datums uit beide tabellen te maken. Zoek dan voor elke dergelijke datum de volgende datum (in dit specifieke geval zijn de datums gegroepeerd per staat, district, en de volgende datum wordt gezocht voor een bepaalde staat, district).
Dus nu hebben we een lijst met bereiken die we zoeken. Nu kunnen we (voor deze specifieke taak links join) andere tabellen samenvoegen met de vereiste voorwaarden:

select
    r.state,
    c.start_cong,
    c.end_cong,
    c.party,
    coalesce(c.district, d.district) district,
    d.start_dist,
    d.end_dist,
    start_comb,
    end_comb,
    case when d.district is not null then start_comb end final_start,
    case when d.district is not null then end_comb end final_end
from (
    with dates as (
        select
            *
        from (
            SELECT 
                c.state,
                c.district,
                start_cong date
            FROM congressperson c
            union 
            SELECT
                c.state,
                c.district, 
                end_cong
            FROM congressperson c
            union 
            SELECT 
                d.state,
                d.district,
                start_dist
            FROM district d 
            union 
            SELECT
                d.state,
                d.district, 
                end_dist
            FROM district d 
        ) DATES
        group by 
            state,
            district,
            date
        order by 
            state,
            district,    
            date
    ) 
    select
        dates.state,
        dates.district,
        dates.date start_comb,
    (select 
        d.date 
    from 
        dates d
    where
        d.state = dates.state and
        d.district = dates.district and
        d.date > dates.date
    order by 
        d.date
    limit 1
    ) end_comb
    from 
        dates) r
left join congressperson c on 
                            c.state = r.state and
                            c.district = r.district and
                            start_comb between c.start_cong and c.end_cong and 
                            end_comb between c.start_cong and c.end_cong
left join district d on 
                        d.state = r.state and
                        d.district = r.district and
                        start_comb between d.start_dist and d.end_dist and 
                        end_comb between d.start_dist and d.end_dist
where
    end_comb is not null 
order by 
    r.state, coalesce(c.district, d.district), start_comb, end_comb, start_cong, end_cong