Обсуждение: translation from ORACLE

I try to translate a database from Oracle to Postgress. for this reason, i search 3 functions :
nvl, max and to_char.

ORACLE : ex : EXEC SQL SELECT nvl (attribut, "defaultString") INTO : vattribut FROM ... : if there
is no attribut satisfying the select vattribut will be equal to attribut , else vattribut will be
equal to attribut.                       EXEC SQL SELECT max(attribut) .... will give the bigger attribut.
        EXEC SQL SELECT to_char(attribut, 'DD-MM-YYYY') ... attribut will be a
 
string in the form '01-02-99'

I didn't find this 3 functions in Postgress, can you give me them and their syntax. thanks.
--
Christine