Answer Posted / sushant butta

Check the answer in detail here. http://www.oraclebin.com/2012/12/what-is-difference-between-tochar-and.html

A lot of people have confusion about the usage of to_char and to_date functions. When to use to_char and when to use to_date. Here I am going to tell you how to do that. I will be discussing to_char function with respect to date only and not with numbers.

Syntax
to_char(value , format_mask)

to_date(string , format_mask)

So when you want to convert a date to a string use to_char function. Always remember that INPUT to to_char function is always a date (excluding numbers here). A format mask over here decides how OUTPUT of to_char function will look. Lets consider this with an example.



sql > Select to_char(sysdate,'DD-MM-YYYY') from dual;

Output : 01-01-2001

INPUT -> sysdate ( a date)
OUTPUT -> 01-01-2001 ( DD-MM-YYYY the format mask)

And when you want to convert a string to a date use to_date function. Always remember that OUTPUT of to_date function is always a date. A format mask over here decides what will the format of INPUT string. Lets have an example.

sql > select to_date( '01-01-2001','DD-MM-YYYY') from dual;

Output : 01-JAN-01

INPUT -> 01-01-2001 ( format_mask is 'DD-MM-YYYY')
OUTPUT -> 01-JAN-01 ( a date, the format here is the default NLS setting for your date)


Just remember the input and output of these functions and you will never make a mistake.

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