SQL tunning

Hi 

Following SQL runs about 8 hours in the database and it is extremely slow when compared with the required speed. 

Can you give some suggestions to improve this please?

SELECT ces.EVENT_SOURCE||'|'||acc.account_num ||'|'|| sub.subscription_id||'|'|| pk.package_name||'|'|| TO_CHAR(chpk.st

art_dat,'ddmmyyyy')

FROM CUSTEVENTSOURCE ces,CUSTHASPRODUCT chpr,CUSTHASPACKAGE chpk,PACKAGE pk,CATALOGUECHANGE cat,ACCOUNT acc, MBTL_SUBSC

RIPTIONINFO sub 

WHERE (ces.CUSTOMER_REF =chpr.CUSTOMER_REF AND ces.EVENT_TYPE_ID=1 )  

AND (chpk.CUSTOMER_REF=chpr.CUSTOMER_REF AND chpr.PRODUCT_SEQ=ces.product_seq AND chpr.PACKAGE_SEQ=chpk.PACKAGE_SEQ AND