Sybase IQ supports zero-length VARCHAR data. If the length of a VARCHAR cell is zero and the cell is not NULL, you get a zero-length cell.
For all other data types, if the length of the cell is zero, Sybase IQ inserts a NULL.
This treatment of zero-length character data is ANSI behavior. If you require non-ANSI behavior, see the NON_ANSI_NULL_VARCHAR option in Reference: Statements and Options.