SQL to C: Binary

The identifiers for the binary ODBC SQL data types are:

SQL_BINARY

SQL_VARBINARY

SQL_LONGVARBINARY

The following table shows the ODBC C data types to which binary SQL data may be converted. For an explanation of the columns and terms in the table, see Converting Data from SQL to C Data Types.

C type identifier	Test	*TargetValuePtr	*StrLen_or_IndPtr	SQLSTATE
SQL_C_CHAR	(Byte length of data) * 2 < BufferLength (Byte length of data) * 2 >= BufferLength	Data Truncated data	Length of data in bytes Length of data in bytes	n/a 01004
SQL_C_WCHAR	(Character length of data) * 2 < BufferLength (Character length of data) * 2 >= BufferLength	Data Truncated data	Length of data in characters Length of data in characters	n/a 01004
SQL_C_BINARY	Byte length of data <= BufferLength Byte length of data > BufferLength	Data Truncated data	Length of data in bytes Length of data in bytes	n/a 01004

When binary SQL data is converted to character C data, each byte (8 bits) of source data is represented as two ASCII characters. These characters are the ASCII character representation of the number in its hexadecimal form. For example, a binary 00000001 is converted to "01" and a binary 11111111 is converted to "FF".

The driver always converts individual bytes to pairs of hexadecimal digits and terminates the character string with a null byte. Because of this, if BufferLength is even and is less than the length of the converted data, the last byte of the *TargetValuePtr buffer is not used. (The converted data requires an even number of bytes, the next-to-last byte is a null byte, and the last byte cannot be used.)

Note

Application developers are discouraged from binding binary SQL data to a character C data type. This conversion is usually inefficient and slow.