oracle - How to extract week number in sql -


i have transdate column of varchar2 type has following entrees

01/02/2012 01/03/2012 

etc.

i converted in date format in column using to_date function. format got.

01-jan-2012 03-apr-2012 

when i'm trying extract weekno, i'm getting null values.

select to_char(to_date(transdate), 'w') weekno tablename.

null null 

how weekno date in above format?

after converting varchar2 date true date datatype, convert varchar2 desired mask:

to_char(to_date('01/02/2012','mm/dd/yyyy'),'ww') 

if want week number in number datatype, can wrap statement in to_number():

to_number(to_char(to_date('01/02/2012','mm/dd/yyyy'),'ww')) 

however, have several week number options consider:

ww  week of year (1-53) week 1 starts on first day of year , continues seventh day of year. w   week of month (1-5) week 1 starts on first day of month , ends on seventh. iw  week of year (1-52 or 1-53) based on iso standard. 

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