text: // The contents of this file are in the public domain. See LICENSE_FOR_EXAMPLE_PROGRAMS.txt
  
  /*
      This example gives a quick overview of dlib's C++ API for the popular SQLite library.
  */
  
  
  #include <iostream>
  #include <dlib/sqlite.h>
  #include <dlib/matrix.h>
  
  using namespace dlib;
  using namespace std;
  
  // ----------------------------------------------------------------------------------------
  
  bool table_exists (
      database& db,
      const std::string& tablename
  )
  {
      // Sometimes you want to just run a query that returns one thing.  In this case, we
      // want to see how many tables are in our database with the given tablename.  The only
      // possible outcomes are 1 or 0 and we can do this by looking in the special
      // sqlite_master table that records such database metadata.  For these kinds of "one
      // result" queries we can use the query_int() method which executes a SQL statement
      // against a database and returns the result as an int.
      return query_int(db, "select count(*) from sqlite_master where name = '"+tablename+"'")==1;
  }
  
  // ----------------------------------------------------------------------------------------
  
  int main() try
  {
      // Open the SQLite database in the stuff.db file (or create an empty database in
      // stuff.db if it doesn't exist).
      database db("stuff.db");
  
      // Create a people table that records a person's name, age, and their "data".
      if (!table_exists(db,"people"))
          db.exec("create table people (name, age, data)");
  
  
      // Now let's add some data to this table.  We can do this by making a statement object
      // as shown.  Here we use the special ? character to indicate bindable arguments and
      // below we will use st.bind() statements to populate those fields with values.  
      statement st(db, "insert into people VALUES(?,?,?)");
  
      // The data for Davis
      string name = "Davis";
      int age = 32;
      matrix<double> m = randm(3,3); // some random "data" for Davis
  
      // You can bind any of the built in scalar types (e.g. int, float) or std::string and
      // they will go into the table as the appropriate SQL types (e.g. INT, TEXT).  If you
      // try to bind any other object it will be saved as a binary blob if the type has an
      // appropriate void serialize(const T&, std::ostream&) function defined for it.  The
      // matrix has such a serialize function (as do most dlib types) so the bind below saves
      // the matrix as a binary blob.
      st.bind(1, name);
      st.bind(2, age);
      st.bind(3, m); 
      st.exec(); // execute the SQL statement.  This does the insert.
  
  
      // We can reuse the statement to add more data to the database.  In fact, if you have a
      // bunch of statements to execute it is fastest if you reuse them in this manner. 
      name = "John";
      age = 82;
      m = randm(2,3); 
      st.bind(1, name);
      st.bind(2, age);
      st.bind(3, m); 
      st.exec();
      
  
  
      // Now lets print out all the rows in the people table.
      statement st2(db, "select * from people");
      st2.exec();
      // Loop over all the rows obtained by executing the statement with .exec().
      while(st2.move_next())
      {
          string name;
          int age;
          matrix<double> m;
          // Analogously to bind, we can grab the columns straight into C++ types.  Here the
          // matrix is automatically deserialized by calling its deserialize() routine.
          st2.get_column(0, name);
          st2.get_column(1, age);
          st2.get_column(2, m);
          cout << name << " " << age << "\n" << m << endl << endl;
      }
  
  
  
      // Finally, if you want to make a bunch of atomic changes to a database then you should
      // do so inside a transaction.  Here, either all the database modifications that occur
      // between the creation of my_trans and the invocation of my_trans.commit() will appear
      // in the database or none of them will.  This way, if an exception or other error
      // happens halfway though your transaction you won't be left with your database in an
      // inconsistent state.  
      // 
      // Additionally, if you are going to do a large amount of inserts or updates then it is
      // much faster to group them into a transaction.  
      transaction my_trans(db);
  
      name = "Dude";
      age = 49;
      m = randm(4,2); 
      st.bind(1, name);
      st.bind(2, age);
      st.bind(3, m); 
      st.exec();
  
      name = "Bob";
      age = 29;
      m = randm(2,2); 
      st.bind(1, name);
      st.bind(2, age);
      st.bind(3, m); 
      st.exec();
  
      // If you comment out this line then you will see that these inserts do not take place.
      // Specifically, what happens is that when my_trans is destructed it rolls back the
      // entire transaction unless commit() has been called.
      my_trans.commit();
  
  }
  catch (std::exception& e)
  {
      cout << e.what() << endl;
  }
  
  // ----------------------------------------------------------------------------------------
  
  
  