readme_example.cc

#include<iostream>
#include <sqlite_modern_cpp.h>
using namespace  sqlite;
using namespace std;

int main() {

	try {
		// creates a database file 'dbfile.db' if it does not exists.
		database db(":memory:");

		// executes the query and creates a 'user' table
		db <<
			"create table if not exists user ("
			"   _id integer primary key autoincrement not null,"
			"   age int,"
			"   name text,"
			"   weight real"
			");";

		// inserts a new user record.
		// binds the fields to '?' .
		// note that only types allowed for bindings are :
		//      int ,long, long long, float, double
		//      string , u16string
		// sqlite3 only supports utf8 and utf16 strings, you should use std::string for utf8 and std::u16string for utf16.
		// note that u"my text" is a utf16 string literal of type char16_t * .
		db << "insert into user (age,name,weight) values (?,?,?);"
			<< 20
			<< u"bob"
			<< 83.25;

		int age = 22;
		float weight = 68.5;
		string name = "jack";
		db << u"insert into user (age,name,weight) values (?,?,?);" // utf16 query string
			<< age
			<< name
			<< weight;

		cout << "The new record got assigned id " << db.last_insert_rowid() << endl;

		// slects from user table on a condition ( age > 18 ) and executes
		// the lambda for each row returned .
		db << "select age,name,weight from user where age > ? ;"
			<< 21
			>> [&](int _age, string _name, double _weight) {
				if(_age != age || _name != name) 
					exit(EXIT_FAILURE);
				cout << _age << ' ' << _name << ' ' << _weight << endl;
		};
		for(auto &&[_age, _name, _weight] : (db << "select age,name,weight from user where age > ? ;" << 21).as<int, string, double>()) {
			if(_age != age || _name != name) 
				exit(EXIT_FAILURE);
			cout << _age << ' ' << _name << ' ' << _weight << endl;
		}

		for(auto &&[_age, _name, _weight] : as<int, string, double>(db << "select age,name,weight from user where age > ? ;" << 21)) {
			if(_age != age || _name != name) 
				exit(EXIT_FAILURE);
			cout << _age << ' ' << _name << ' ' << _weight << endl;
		}

		// selects the count(*) from user table
		// note that you can extract a single culumn single row result only to : int,long,long,float,double,string,u16string
		int count = 0;
		db << "select count(*) from user" >> count;
		cout << "cout : " << count << endl;

		// you can also extract multiple column rows
		db << "select age, name from user where _id=1;" >> tie(age, name);
		cout << "Age = " << age << ", name = " << name << endl;

		// this also works and the returned value will be automatically converted to string
		string str_count;
		db << "select count(*) from user" >> str_count;
		cout << "scount : " << str_count << endl;
	}
	catch (exception& e) {
		cerr << e.what() << endl;
		exit(EXIT_FAILURE);
	}

  return 0;
}