Dates where day/month is unknown

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Hi

I got an unexpected problem - I have dates, some of which are only
years, others have a month and a year and the rest day, month and
year. I INSERT these dates as follows (which works fine):

INSERT .... to_date('12 1966', 'mm yyyy'), to_date('1984', 'yyyy')
......

However, I cannot retrieve the dates without knowing the format
in which they were inserted. For example, if just the year was
inserted (e.g., 1984) and I retrieve the date - I get 01 Aug 1984 
(which is plain not true). What I expect is white space when
the day and month is unknown (and was not inserted). The SELECT
statement I used were of the form to_char(date1,'dd Mon yyyy').

Is there a simple solution to this problem? I just want to get
back the information I inserted - nothing more! 

- Andrew
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Andrew Deacon                       email:  deacon_at_inf.ethz.ch
Institut fur Informationssysteme    
Departement Informatik              Phone:  +41 1 254 72 72
ETH-Zentrum, CH-8092 Zuerich        Fax  :  +41 1 262 39 73