Clickhouse SQL查询技巧

clickhouse 在关联不上的情况会返回0值，而不是MySQL返回Null

select *  from
   (select 1 as a union all
    select 2  as a union all
    select 3  as a union all
    select 0  as a union all
    select 0  as a) x
left join (
select 2  as b, 'adc' as c union all
    select 3  as b, 'adc' as c union all
    select 5  as b, 'adc' as c union all
    select 0  as b, 'adc' as c union all
    select 0  as b, 'adc' as c
           ) y on x.a = y.b
-- where c= ''
order by a