Lesson_01/Task_3/Task_3.cpp - master - AirLexa/07

Lesson_01/Task_3/Task_3.cpp
92 строки3 KB
AirLexa
урок 1
23 июн 2026, 16:30
23 июн 2026, 16:30ee26e4f
#include <iostream>
#include <windows.h>
#include <string>
#include <sstream>
#include <vector>
#include <map>

class SqlSelectQueryBuilder {
private:
    std::string str_column = "";
    std::string str_from = "";
    std::string str_where = "";

public:
    SqlSelectQueryBuilder& AddColumn(const std::string& column) {
        if (!str_column.empty()) str_column.append(", ");
        str_column.append(column);
        return *this;
    }

    SqlSelectQueryBuilder& AddColumns(const std::vector<std::string>& columns) noexcept
    {
        for (std::string s : columns)
            AddColumn(s);
        return *this;
    }

    SqlSelectQueryBuilder& AddFrom(const std::string& from) {
        str_from = from;
        return *this;
    }

    SqlSelectQueryBuilder& AddWhere(const std::string& w1, const std::string& w2) {
        if (!str_where.empty()) str_where.append(" AND ");
        str_where.append(w1).append("=").append(w2);
        return *this;
    }

    SqlSelectQueryBuilder& AddWhere(const std::string& w1, 
        const std::string& w2, const std::string& mark) {
        if (!str_where.empty()) str_where.append(" AND ");
        str_where.append(w1).append(mark).append(w2);
        return *this;
    }

    SqlSelectQueryBuilder& AddWhere(const std::map<std::string, std::string>& kv) noexcept
    {
        for (const auto& [w1, w2] : kv)
            AddWhere(w1, w2);
        return *this;
    }

    std::string build() {
        if (str_from.empty()) return "";
        std::stringstream query;
        query << "SELECT " << (str_column.empty() ? "*" : str_column) <<
            " FROM " << str_from;
        if (!str_where.empty())
            query << " WHERE " << str_where;
        return query.str().append(";");
    }
};

class AdvancedSqlSelectQueryBuilder : public SqlSelectQueryBuilder {
public:    
    AdvancedSqlSelectQueryBuilder& AddWhereMore(const std::string& w1, const std::string& w2) noexcept
    {
        SqlSelectQueryBuilder::AddWhere(w1, w2, ">");
        return *this;
    }

    AdvancedSqlSelectQueryBuilder& AddWhereLess(const std::string& w1, const std::string& w2) noexcept
    {
        SqlSelectQueryBuilder::AddWhere(w1, w2, "<");
        return *this;
    }
};

int main()
{
    SetConsoleCP(1251);
    SetConsoleOutputCP(1251);

    AdvancedSqlSelectQueryBuilder query_builder;
    query_builder.AddColumn("name").AddColumn("phone");
    query_builder.AddFrom("students");
    query_builder.AddWhereMore("id", "21").AddWhereLess("id", "42").AddWhere("name", "John");

    std::string s = query_builder.build();

    std::cout << "SQL = " << s << std::endl;
}