C++ class for managing the access to database - c++

Question

The question is more a Best way of doing question than a real problem.
Context and what I'm doing
I have an application that must access to the database. Therefore I have a class DatabaseManager that is called every time I need to access the database and which does for instance:
DatabaseManager *db = new DatabaseManager;
std::vector<Element> elementVector = db->getAElementsById(id);
And you the same for all insert, update or remove requests.
What eventually happened...
...is that my file has already 1200 lines and is growing with every new feature.
The question
So how do pretty people do ?
One header several splitted files? (This told that it's not a good idea)
Splitting the class in several class? The databaseManager is one class, it would be a nonsense...
Is there any other option? (I'm not familiar with the notion of namespace, maybe is it a way?)
I read also other post but didn't find either the good question to ask google, or people answering my question.

Answer 1

I have my database module split into more than one file. For example, one file handles insertions, another file handles extractions and a third handles searches.
Mine is actually more complex, but the practice should be to split up the code into separate themed files, preferably no more than 300 LOC (Lines Of Code).

Answer 2

The solution I chose for now is the following (because I was too lazy to reconstruct new classes and so on) : I splitted the class in several cpp files
// DatabaseManager.h
class DatabaseManager
{
//// Getters - in DatabaseManager_getters.cpp
public:
// Movies
Movie getOneMovieById(const int id);
QList<Movie> getAllMovies(const QString fieldOrder = "title");
....
private:
// Other functions for getters
Movie hydrateMovie(QSqlQuery &query);
//// Inserts - in DatabaseManager_insert.cpp
public:
bool insertNewMovie(Movie &movie);
....
private:
bool insertNewTag(Tag &tag);
....
//// Updates - in DatabaseManager_update.cpp
public:
bool updateMovie(Movie &movie);
....
//// Delete - in DatabaseManager_delete.cpp
public:
bool deleteMovie(Movie &movie);
private:
bool deletePeople(const People &people);
};
And obviously the .cpp files are following what announced. It's easier for me to find where a function is and to maintain the code.
Another time, I'll think twice if it's not more relevant to follow the advices you gave.
Thx again !