now i know how to use one-to-one, many-to-one, many-to-many, but i dont know how to search a record.
where can i get the example for this?
....
i read the documentation before, but i dont understant.
select cat from CAt as cat,
what is cat and what is Cat?

cat is an alias (shortname) as it is on SQL : you set it and use it in the query, Cat is the mapped class (you can use full name of the class too: eg.Cat).

thanks for helping.
.......

for example, i have 2 class in one2one relation
Student.java and Address.java

Student.java
-- id
-- name

Address
-- id
-- name

how can i retrieve the record?
in sql, that is simple,
select * from student where addre='? ';

but in hql....

actually, i'm not very good in sql language. i learn java just 2 months only. java is oo but mysql not, so i search some information from internet, then i know O/R mapping.

where :address is a named parameter.
Notice the dot between student and address. This is an Object oriented query language.

I suggest you to read the Hibernate reference guide tons of time and play with very simple example. This is the best way to learn. You'll find the reference guide difficult and obscure. Actually it's very rich and it takes time to understand everything (I still learn when I read it).
Have a look at the External ducmentation, especially tutorials.

Thank you very much.
i will study the reference document and try to find some case study.