google bigquery - Debugging SQL join each statement -

i wondering how debug sql join each statement. please provide useful techniques, referring code below:

select tat.*,claim.masc_nm,       claim.country,claim.carrier_model        x tat join  each      (       (select claim_num, masc_nm masc_nm, country,         carrier_model y claims upload_dt>='2014-01-01'         group  claim_num, masc_nm, country, carrier_model) claim        left join z          on tat.claim_num=claim.claim_num 

for starter, make sure each join statement has "on" statement