class IDatabase{
    virtual void execute(const char* statement) = 0;
    virtual void beginTransaction() = 0;
    virtual void commitTransaction() = 0;
    virtual void rollbackTransaction() = 0;
}

void initialize_db(IDatabase* db){
    db->beginTransaction();
    db->execute("CREATE TABLE foo ...");
    ...
    db->commitTransaction();
}

class MysqlDatabase: public IDatabase { ...

class MockDatabase: public IDatabase { ...

class SQLiteDatabase: public IDatabase { ...

========================

struct DatabaseVtable{
    void (*execute) (void*, const char* statement);
    void (*beginTransaction)(void*);
    void (*commitTransaction)(void*);
    void (*rollbackTransaction)(void*);
};

struct Database{
    const DatabaseVTable* vt;
};

void initialize_db(Database* db){
    db->vt->beginTransaction(db);
    db->vt->execute(db, "CREATE TABLE foo ...");
    ...
    db->vt->commitTransaction(db);
}



const DatabaseVtable MysqlDatabaseVTable = {
    &mysql_execute,
    &mysql_beinTransaction,
    ...
};

struct MysqlDatabase{
    const DatabaseVTable* vt;
    mysql_connection_t conn;
}

void init_mysql_db(MysqlDatabase* db){
    db->vt = &MysqlDatabaseVTable;
    ....
}