Re: [sqlite] C++ - HOW MANY rows?

[Black, Michael (IS)]

Try using this method...you just need to ensure mystmt is set to NULL to start 
with and reset to NULL in finalize().


const int mySQLite3::read_int(int pos)
throw(somexception) {
    if (mystmt == NULL) { // Ensure mystmt is set to NULL in constructor
      rc = sqlite3_prepare_v2(db, SQLStatement.c_str(), -1, &mystmt, NULL);
      if(rc != SQLITE_OK) {
          try {
              this->display(rc, FILE, METHOD, LINE);
          } catch(somexception e) {
              throw e;
          }
      }
    } 
    rc = sqlite3_step(mystmt);
    if(rc == SQLITE_ROW ) {
        apint = sqlite3_column_int(mystmt,pos);
        counter++;
        return apint;
    }
    if (rc != SQLITE_DONE) {
      this->display(rc,FILE,METHOD,LINE+":"+sqlite3_errmsg(db));
    }

    try {
        this->finalize(); // ensure mystmt set to null in finalize
    } catch(somexception& e) {
        throw e;
    }
    return -1; // how do you know when you're done? Will -1 work?
}


Michael D. Black
Senior Scientist
Advanced Analytics Directorate
Advanced GEOINT Solutions Operating Unit
Northrop Grumman Information Systems

________________________________________
From: sqlite-users-boun...@sqlite.org [sqlite-users-boun...@sqlite.org] on 
behalf of Arbol One [arbol...@gmail.com]
Sent: Tuesday, September 11, 2012 9:44 PM
To: 'General Discussion of SQLite Database'
Subject: EXT :Re: [sqlite] C++ - HOW MANY rows?

Thanks Igor for your prompt response.
Since the call to the sqlite3_step function is inside the mySQLite3::read_*
class-function/method, I call the read_* method from Runner::read_tblName()
for each datum I need to retrieve. Now, in a while loop inside
Runner::read_tblName() I could call the mySQLite3::read_* for the data to be
retrieved, but instead of reading the next row of data, it keeps on reading
the same row again and again. Furthermore, I have no way to let
Runner::read_tblName 'know' that there is no more data, hence stopping the
while loop.
Obviously my problem is in design, but I don't have enough experience using
SQLite3 to come up with a better idea.
My question is, really, how do you, C++ programmers, have resolved this
issue? There must be a solution.
void Runner::read_tblName() {
   .
    sql_statement = "SELECT * FROM name";
//while(there is more data){
// I have no-way to report to this method that there is no more data in the
bank
// I could add a flag to the mySQLite3 class and have the while loop check
on its status,
// or a signal that would be trigger by the ending of the while loop.

    db->setStmt(sql_statement);
    int pos = 0;
    data1 = db->read_int(pos);

    db->setStmt(sql_statement);
    pos = 1;
    data2 = db->read_str(pos);
    data3 = db->read_str(++pos);
    data4 = db->read_str(++pos);
    data5 = db->read_str(++pos);

    Glib::ustring str;
    str = apstr.format(data1);
    str += " ";
    str += data2;
    str += ". ";
    str += data3;
    str += " ";
    str += data4;
    str += " ";
    str += data5;
    apex->setException(str, FILE, METHOD, LINE);
    apex->Display();
// } <<<---

}
const int mySQLite3::read_int(int pos)
throw(somexception) {
    rc = sqlite3_prepare_v2(db, SQLStatement.c_str(), -1, &mystmt, NULL);
    if(rc != SQLITE_OK) {
        try {
            this->display(rc, FILE, METHOD, LINE);
        } catch(somexception e) {
            throw e;
        }
    } else {
        counter++;
    }
    rc = sqlite3_step(mystmt);
    if(rc == SQLITE_ROW ) {
        apint = sqlite3_column_int(mystmt,pos);
    }

    try {
        this->finalize();
    } catch(somexception& e) {
        throw e;
    }
    return apint;
}
const Glib::ustring& mySQLite3::read_str(const int pos)
throw(somexception) {

     //if(pos == 0) {
        rc = sqlite3_prepare_v2(db, this->SQLStatement.c_str(), -1, &mystmt,
NULL);
     //}
    if(rc != SQLITE_OK) {
        try {
            this->display(rc, FILE, METHOD, LINE);
        } catch(somexception e) {
            throw e;
        }
    } else {
        counter++;
    }

    rc = sqlite3_step(mystmt);

    if(rc == SQLITE_ROW ) {
        apstr = (const char*)sqlite3_column_text(mystmt,pos);
    }
    try {
        this->finalize();
    } catch(somexception& e) {
        throw e;
    }
    return apstr;

}

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