Parameter-value type array
The parameter-value type array, types, is the eighth argument of the mi_exec_prepared_statement() and mi_open_prepared_statement() functions.
Each element of the parameter-value type array is a pointer to a string that identifies the data type of the input-parameter value. The type names must match those that the mi_type_typename() function would generate for the data type.
If the prepared statement has input parameters and is not an INSERT statement, you must use the types array to supply the data types of the input parameters. Otherwise, you can pass in a NULL-valued pointer as the types argument.