Looking for one liner example how to bind and insert a null value into a database using ODBC API

问题

The function is

SQLRETURN SQLBindParameter(
      SQLHSTMT        StatementHandle,
      SQLUSMALLINT    ParameterNumber,
      SQLSMALLINT     InputOutputType,
      SQLSMALLINT     ValueType,
      SQLSMALLINT     ParameterType,
      SQLULEN         ColumnSize,
      SQLSMALLINT     DecimalDigits,
      SQLPOINTER      ParameterValuePtr,
      SQLLEN          BufferLength,
      SQLLEN *        StrLen_or_IndPtr);

The documentations I have seen is confusing. Do the srguments depend on the data type or not I found an example here http://support.microsoft.com/kb/248799 which does not seem to work on DB2. I thought odbc was consistent across databases. A specific code example would he helpful.

回答1:

Its not one line as such but

SQLLEN ival;

ret = SQLBindParameter( stmt, 1, SQL_PARAM_INPUT, SQL_C_CHAR, SQL_VARCHAR, 100, 0, NULL, 0, &ival );

/*
 * before execution is called
 */

ival = SQL_NULL_DATA;

That inserts a NULL value as a CHAR(100) datatype. Pick the actual datatype to match what your column type is, but the important thing is to set the indicator value to SQL_NULL_DATA before the SQLExecute or SQLExecDirect is called. And make sure its still set to that value at the execute point.

来源：https://stackoverflow.com/questions/6486746/looking-for-one-liner-example-how-to-bind-and-insert-a-null-value-into-a-databas