C++ and sqlite3- sqlite3_prepare_v2 is not working - c++

Question

I'm using sqlite3 with C++ . But the problem is that when I debugged the code I realised that it does not, I mean sqlite3_prepare_v2 does not extract the data from the database.
When I printed the value it extracted, it printed some garbage value. At the same time, I noticed the following warning:
Warning 4 warning LNK4248: unresolved typeref token (01000028) for
'sqlite3_stmt'; image may not run .
I'm working on MS visual studio 2010 windows forms application.
Can anyone help?

Answer 1

I think the linker complaint is ok. See http://social.msdn.microsoft.com/Forums/en-US/8376b2f0-cc36-48c8-9021-f30bda41f410/linker-warning-lnk4248-possible-problem
The following does not take into account that you're programming in MS managed C++, however, I hope it still provides some guidance.
sqlite3_prepare_v2 prepares the statement but does not execute anything.
You need to call sqlite3_step to execute (or partly execute) the SQL.
For an SQL statement that returns nothing (e.g. UPDATE, DELETE, INSERT) you call sqlite3_step once and it should return SQLITE_DONE if it worked.
For a statement that can return multiple rows you call sqlite3_step repeatedly. Each time the return code is SQLITE_ROW you have been returned a row of data that you can access with the
sqlite3_column_* set of statements. When all data has been returned sqlite3_step returns SQLITE_DONE.
Code might look something like this
sqlite3* db;
int rc = sqlite3_open(databasePath.c_str(), &db);
std::string sql = "SELECT Id, Url FROM Url WHERE Page_Download_Reqd <> 0;";
sqlite3_stmt* statementPtr;
const char* tailPtr;
int rc = sqlite3_prepare_v2(db, sql.c_str(), sql.size(), &statementPtr, &tailPtr);
bool finished = false;
do {
int rc = sqlite3_step(statementPtr);
switch (rc) {
case SQLITE_ROW: {
__int64 id = sqlite3_column_int(statementPtr, 0);
std::string url = reinterpret_cast<const char*>(sqlite3_column_text(statementPtr, 1));
// Do something with your data
}
break;
case SQLITE_DONE:
finished = true;
break;
default:
assert(false);
}
} while (!finished);
If you have variables in you SQL, e.g.
SELECT Id, Url FROM Url WHERE Count <> :count;
then you need to use one of the sqlite3_bind_* functions between the sqlite3_prepare_v2 and sqlite3_step functions. For example
__int count = 6;
std::string bindVarName = ":count";
rc = sqlite3_bind_int(
statementPtr,
sqlite3_bind_parameter_index(statementPtr, bindVarName.c_str()),
count);