update.h

C++实现简单数据库管理系统

#ifndef _UPDATE_H
#define _UPDATE_H
#include "common.h"

int  update(const char* update_path)
{
	ifstream in;
	in.open(update_path);
	if (!in.is_open())
	{
		cerr<<"can't open the file\n";
		return 0;//can't open the file
	}


	string create_cmd="",temp;
	bool right=false;// check the format

	while(getline(in,temp))create_cmd+=" "+temp;//get all the string in the create file
	//cout<<create_cmd;
	in.close();

	string::const_iterator beg = create_cmd.begin();
	string::const_iterator end = create_cmd.end();
	smatch result;
	const string total("\\s*update\\s+(\\w+)\\s+set\\s+(\\w+)\\s*=\\s*(\\w+)\\s*where\\s*(\\w+)\\s*=\\s*(\\w+)\\s+(\\w+)\\s+(\\w+)\\s*=\\s*(\\w+)\\s*$");
	regex reg(total);
	string table_name,set_column_name,set_column_value,condition,column_1,column_1_value;
	string column_2,column_2_value;
	while(regex_search(beg, end, result, reg))
	{
		table_name = result[1].str();
		set_column_name = result[2].str();
		set_column_value = result[3].str();
		column_1 = result[4].str();
		column_1_value = result[5].str();
		condition = result[6].str();
		column_2 = result[7].str();
		column_2_value = result[8].str();


		cout<<table_name<<set_column_name<<set_column_value<<column_1<<"\n";
		cout<<column_1_value<<condition<<column_2<<column_2_value<<"\n";
		beg = result[0].second;
		right=true;

	}
	return 1;
}
#endif