SQL & PL/SQL

Sorry to bother you with this newbie-type of question, but I cannot find a suitable solution for my problem.

I'm porting a MySQL Script to Oracle's SQL script and got the following problem: how can I express the following line of code in the Oracle accent? The calendarweek can be expressed by "TO_CHAR(datetime,'WW')", but isn't there an adequate expression for MySQL's "SELECT function(column) AS new_column FROM source.table" ?

SELECT DATE_FORMAT(datetime, 'WW') AS `CALENDARWEEK` FROM iops.detail;