Several reasons for using varchar2 instead of char: 1. char (xx) will always rpad data with blanks. This is a guarantee for surprises when comparing data and using indexes for searches because implicit conversion strikes. Please look up the rules for implicit conversions. 2. A value of char will always consume full space in the database because it is padded. Therefore, indexes grow bigger and searches are slower. 3. As opposed to a wide-spread misunderstanding, char (1) does *not* use less space in the database than varchar2 (1) when the value 'a' is stored because also char (1) has a length field. This can be proved by the dump () function.
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