Qt 5.9 | Qt SQL | Books | initdb.h Example File

Qt 5.9.9 Reference Documentation

# initdb.h Example File

books/initdb.h

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      #ifndef INITDB_H
      #define INITDB_H

      #include <QtSql>

      void addBook(QSqlQuery &q, const QString &title, int year, const QVariant &authorId,
                   const QVariant &genreId, int rating)
      {
          q.addBindValue(title);
          q.addBindValue(year);
          q.addBindValue(authorId);
          q.addBindValue(genreId);
          q.addBindValue(rating);
          q.exec();
      }

      QVariant addGenre(QSqlQuery &q, const QString &name)
      {
          q.addBindValue(name);
          q.exec();
          return q.lastInsertId();
      }

      QVariant addAuthor(QSqlQuery &q, const QString &name, const QDate &birthdate)
      {
          q.addBindValue(name);
          q.addBindValue(birthdate);
          q.exec();
          return q.lastInsertId();
      }

      QSqlError initDb()
      {
          QSqlDatabase db = QSqlDatabase::addDatabase("QSQLITE");
          db.setDatabaseName(":memory:");

          if (!db.open())
              return db.lastError();

          QStringList tables = db.tables();
          if (tables.contains("books", Qt::CaseInsensitive)
              && tables.contains("authors", Qt::CaseInsensitive))
              return QSqlError();

          QSqlQuery q;
          if (!q.exec(QLatin1String("create table books(id integer primary key, title varchar, author integer, genre integer, year integer, rating integer)")))
              return q.lastError();
          if (!q.exec(QLatin1String("create table authors(id integer primary key, name varchar, birthdate date)")))
              return q.lastError();
          if (!q.exec(QLatin1String("create table genres(id integer primary key, name varchar)")))
              return q.lastError();

          if (!q.prepare(QLatin1String("insert into authors(name, birthdate) values(?, ?)")))
              return q.lastError();
          QVariant asimovId = addAuthor(q, QLatin1String("Isaac Asimov"), QDate(1920, 2, 1));
          QVariant greeneId = addAuthor(q, QLatin1String("Graham Greene"), QDate(1904, 10, 2));
          QVariant pratchettId = addAuthor(q, QLatin1String("Terry Pratchett"), QDate(1948, 4, 28));

          if (!q.prepare(QLatin1String("insert into genres(name) values(?)")))
              return q.lastError();
          QVariant sfiction = addGenre(q, QLatin1String("Science Fiction"));
          QVariant fiction = addGenre(q, QLatin1String("Fiction"));
          QVariant fantasy = addGenre(q, QLatin1String("Fantasy"));

          if (!q.prepare(QLatin1String("insert into books(title, year, author, genre, rating) values(?, ?, ?, ?, ?)")))
              return q.lastError();
          addBook(q, QLatin1String("Foundation"), 1951, asimovId, sfiction, 3);
          addBook(q, QLatin1String("Foundation and Empire"), 1952, asimovId, sfiction, 4);
          addBook(q, QLatin1String("Second Foundation"), 1953, asimovId, sfiction, 3);
          addBook(q, QLatin1String("Foundation's Edge"), 1982, asimovId, sfiction, 3);
          addBook(q, QLatin1String("Foundation and Earth"), 1986, asimovId, sfiction, 4);
          addBook(q, QLatin1String("Prelude to Foundation"), 1988, asimovId, sfiction, 3);
          addBook(q, QLatin1String("Forward the Foundation"), 1993, asimovId, sfiction, 3);
          addBook(q, QLatin1String("The Power and the Glory"), 1940, greeneId, fiction, 4);
          addBook(q, QLatin1String("The Third Man"), 1950, greeneId, fiction, 5);
          addBook(q, QLatin1String("Our Man in Havana"), 1958, greeneId, fiction, 4);
          addBook(q, QLatin1String("Guards! Guards!"), 1989, pratchettId, fantasy, 3);
          addBook(q, QLatin1String("Night Watch"), 2002, pratchettId, fantasy, 3);
          addBook(q, QLatin1String("Going Postal"), 2004, pratchettId, fantasy, 3);

          return QSqlError();
      }

      #endif