> As I known sqlind is for know if a column allow null values and not
> for know if a column value is null.

In API Reference, p.92 you find:

"The value contained in sqltype provides two pieces of information:

a) The datatype of the parameter or select-list item.

b) Whether sqlind is used to indicate NULL values. If sqlind is used,
its value specifies whether the parameter or select-list item is NULL
(–1), or not NULL (0).

For example, if sqltype equals SQL_TEXT, the parameter or select-list
item is a CHAR that does not use sqlind to check for a NULL value
(because, in theory, NULL values are not allowed for it). If sqltype
equals SQL_TEXT + 1, then sqlind can be checked to see if the
parameter or select-list item is NULL."

So, I understand it as:

a) if (sqltype & 1) == 0, sqldata _cannot_ be null.
b) if (sqltype & 1) == 1 && sqlind == 0, sqldata _is not_ null.
c) if (sqltype & 1) == 1 && sqlind == 1, sqldata _is_ null.

Best regards,
Roman Rokytskyy