如何使用 EXISTS 关键字检查两个表中是否存在对应的值？

select pn_code,serialnumber from pnassertbasic_ruku pr left join pnassertruku pu on pr.parent_pnassertruku_id = pu.child_pnassertrukudetails_id 
where pn_code is not null and serialnumber is not null and date(pr.create_time) = curdate() and pr.warehouseentrynumber <> 'wed3791f0b'

select pn_code,serialnumber from pnassertbasic_ruku pr left join pnassertruku pu on pr.parent_pnassertruku_id = pu.child_pnassertrukudetails_id 
where pu.child_pnassertrukudetails_id is null and pr.warehouseentrynumber = 'wed3791f0b'

select * from (
    select pn_Code,serialNumber from pnassertbasic_ruku pr left join pnassertruku pu on pr.parent_pnAssertRuku_id = pu.child_pnAssertRukuDetails_id 
where pn_Code is not null and serialNumber is not null and DATE(pr.create_time) = CURDATE() and pr.warehouseEntryNumber <> 'WEd3791f0b'
) as temp1 
where EXISTS (
    select * from (
    select pn_Code,serialNumber from pnassertbasic_ruku pr left join pnassertruku pu on pr.parent_pnAssertRuku_id = pu.child_pnAssertRukuDetails_id 
where pu.child_pnAssertRukuDetails_id is null and pr.warehouseEntryNumber = 'WEd3791f0b'
    ) as temp2
    where temp1.pn_Code = temp2.pn_Code and temp1.serialNumber = temp2.serialNumber 
)