CODEWITHSUNDEEP
c++mysqlsortingvector
Brian Dela Cruz
Brian Dela Cruz

Reputation: 103

In C++ how do I store an SQL query and sort it?

I have a wine database that I am trying to retrieve data from, to store in a vector and sort for structure. I can't seem to understand how to store an sql query in c++, I have the command that selects the whole table and a while loop that processes the rows but how in the world do save the results of the query. More specifically how would I store the query in a vector to sort?

Am I overthinking this? I've been pondering and testing different for hours and the logic of combining the two languages is killing me.

Can I sort a whole row? In my code can I sort row[2]? Can I store a whole row to a vector?

Here is my code that has a sql command to get all the wine information from a database. Then there is a while loop to display everything. How do I store everything from the sql_cmd in a vector?

Code

I can specify more and provide more code snippets if you need, let me know if I am still being general.

Upvotes: 0

Views: 2516

Answers (2)

4386427
4386427

Reputation: 44284

You could do

class Wine
{
  public:
    string name;
    string vintage;
    string price;    // Maybe you want to convert to double instead of storing a string
    // and so on
}

vector<Wine> myWines;

In your while loop you could add:

Wine tmp;
tmp.name = row[0];
tmp.vintage = row[1];
// and so on
myWines.push_back(tmp);

Now you can sort by name like this

std::sort(myWines.begin(), myWines.end(),
      [] (Wine const& a, Wine const& b) { return a.name < b.name; });

or by vintage like this

std::sort(myWines.begin(), myWines.end(),
      [] (Wine const& a, Wine const& b) { return a.vintage < b.vintage; });

The sorting can be demonstrated like:

class Wine
{
public:
    string name;
    string vintage;
    string price;    // Maybe you want to convert to double instead of storing a string
    // and so on
};

int main()
{
    vector<Wine> myWines;

    Wine tmp;
    tmp.name = "d";
    tmp.vintage = "3";
    tmp.price = "i";
    myWines.push_back(tmp);

    tmp.name = "g";
    tmp.vintage = "1";
    tmp.price = "f";
    myWines.push_back(tmp);

    tmp.name = "a";
    tmp.vintage = "2";
    tmp.price = "c";
    myWines.push_back(tmp);

    cout << "Unsorted" << endl;

    // Print the vector
    for (auto& v : myWines)
    {
        cout << v.name << " " << v.vintage << " " << v.price << endl;
    }

    cout << "Sort by name" << endl;
    std::sort(myWines.begin(), myWines.end(),
              [] (Wine const& a, Wine const& b) { return a.name < b.name; });

    // Print the vector
    for (auto& v : myWines)
    {
        cout << v.name << " " << v.vintage << " " << v.price << endl;
    }

    cout << "Sort by vintage" << endl;
    std::sort(myWines.begin(), myWines.end(),
          [] (Wine const& a, Wine const& b) { return a.vintage < b.vintage; });

    // Print the vector
    for (auto& v : myWines)
    {
        cout << v.name << " " << v.vintage << " " << v.price << endl;
    }

    return 0;
}

output:

Unsorted
d 3 i
g 1 f
a 2 c
Sort by name
a 2 c
d 3 i
g 1 f
Sort by vintage
g 1 f
a 2 c
d 3 i

Upvotes: 3

Paul Evans
Paul Evans

Reputation: 27577

You want a struct to store your data, something like:

struct Wine {
    Wine(const string& name,
         const string& vintage,
         const string& rating,
         float price,
         const string& type) : name_(name), vintage_(vintage), rating_(rating), price_(price), type_(type) {};
    string name_;
    string vintage_;
    string rating_;
    float price_;
    string type_;
}

vector<Wine> vec;

and then in your loop:

vec.push_back(Wine(row[0],row[1],row[2],row[3],row[4]));

Upvotes: 1

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