scope of an alias in an query using dblink

QUERY A

SELECT DISTINCT A.EMPLID FROM PS_BAS_PARTIC A

WHERE NOT EXISTS (SELECT 'X' FROM SYSADM.PS_RC_CASE@HCMTOCRM

                  WHERE SYSADM.PS_RC_CASE.BO_ID_CUST=

                                        (SELECT SYSADM.PS_RD_PERSON.BO_ID FROM SYSADM.PS_RD_PERSON@HCMTOCRM

                                         WHERE SYSADM.PS_RD_PERSON.EMPLID= A.EMPLID));

QUERY B

SELECT DISTINCT A.EMPLID FROM PS_BAS_PARTIC A

WHERE NOT EXISTS (SELECT 'X' FROM SYSADM.PS_RC_CASE@HCMTOCRM

                  WHERE SYSADM.PS_RC_CASE.BO_ID_CUST=

                                        (SELECT SYSADM.PS_RD_PERSON.BO_ID FROM SYSADM.PS_RD_PERSON@HCMTOCRM

                                         WHERE SYSADM.PS_RD_PERSON.EMPLID=