SQL 多变关联使用子查询去重

不去重状态

select a.*,
       b.recon_amt
from free_settlement_first a
         left join free_settlement_second b on a.settlement_first_id = b.settlement_first_id

有2条数据出现了重复

使用子查询去重

select a.*,
       b.recon_amt
from free_settlement_first a
         left join free_settlement_second b on a.settlement_first_id = b.settlement_first_id
where not exists(select 1
                 from free_settlement_second b2
                 where a.settlement_first_id = b2.settlement_first_id
                   and b.settlement_second_id > b2.settlement_second_id
                )