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SQL to C: Binary

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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.