// 使用 Linq 函数实现 Innerjoin
// 结果 与 InnerJoin() 相同
static void InnerJoinMethod()
{
// 表内交叉
var racers = Formula1.GetChampions().
SelectMany(r => r.Years, (r, y) => new { reacer = r, year = y });
// 表内交叉
var teams = Formula1.GetContructorChampions().
SelectMany(t => t.Years, (t, y) => new { team = t, year = y });
// 两个结果再交叉
var racersAndTeams = racers.Join(teams,
r => r.year,
t => t.year,
(r, t) => new {
Year = r.year,
Champion = r.reacer.FirstName,
Constructor = t.team.Name
}).
OrderBy(y => y.Year).
Take(10);
foreach (var item in racersAndTeams)
{
Console.WriteLine("{0}: {1,-20} {2}",
item.Year, item.Champion, item.Constructor);
}
}
static void GroupJoin()
{
// var q =
//from c in categories
//join p in products on c equals p.Category into ps
//select new { Category = c, Products = ps };
var racers = from r in Formula1.GetChampions()
from y in r.Years
select new
{
Year = y,
Name = r.FirstName + " " + r.LastName
};
var teams = from t in Formula1.GetContructorChampions()
from y in t.Years
select new
{
Year = y,
Name = t.Name
};
var racersAndTeams =
from r in racers
join t in teams on r.Year equals t.Year into ts
select new
{
Year = r.Year,
Racer = r.Name,
Constructor = ts
};
foreach (var r in racersAndTeams)
{
Console.WriteLine("{0} {1}", r.Year, r.Racer);
foreach (var t in r.Constructor)
{
Console.WriteLine("\t{0}", t.Name);
}
}
}
// 内链接, 只包含 Year 相等的两边数据
static void InnerJoin()
{
// 表内交叉
var racers = from r in Formula1.GetChampions()
from y in r.Years
select new
{
Year = y,
Name = r.FirstName + " " + r.LastName
};
// 表内交叉
var teams = from t in Formula1.GetContructorChampions()
from y in t.Years
select new
{
Year = y,
Name = t.Name
};
// 两表交叉
var racersAndTeams =
(from r in racers
join t in teams on r.Year equals t.Year
orderby t.Year
// t 表 teams, r 代表 racers
select new
{
Year = r.Year,
Champion = r.Name,
Constructor = t.Name
}).Take(10); // 只显示前 10 条数据
Console.WriteLine("Year World Champion\t Constructor Title");
foreach (var item in racersAndTeams)
{
Console.WriteLine("{0}: {1,-20} {2}",
item.Year, item.Champion, item.Constructor);
}
}
static void Join()
{
var racers = from r in Formula1.GetChampions()
from y in r.Years
where y > 2003
select new
{
Year = y,
Name = r.FirstName + " " + r.LastName
};
var teams = from t in
Formula1.GetContructorChampions()
from y in t.Years
where y > 2003
select new
{
Year = y,
Name = t.Name
};
var racersAndTeams =
from r in racers
join t in teams on r.Year equals t.Year
select new
{
Year = r.Year,
Racer = r.Name,
Team = t.Name
};
Console.WriteLine("Year Champion " + "Constructor Title");
foreach (var item in racersAndTeams)
{
Console.WriteLine("{0}: {1,-20} {2}",
item.Year, item.Racer, item.Team);
}
}
static void LeftOuterJoin()
{
var racers = from r in Formula1.GetChampions()
from y in r.Years
select new
{
Year = y,
Name = r.FirstName + " " + r.LastName
};
var teams = from t in Formula1.GetContructorChampions()
from y in t.Years
select new
{
Year = y,
Name = t.Name
};
var racersAndTeams =
(from r in racers
join t in teams on r.Year equals t.Year into rt
from t in rt.DefaultIfEmpty()
orderby r.Year
select new
{
Year = r.Year,
Champion = r.Name,
Constructor = t == null ? "no constructor championship" : t.Name
}).Take(10);
Console.WriteLine("Year Champion\t\t Constructor Title");
foreach (var item in racersAndTeams)
{
Console.WriteLine("{0}: {1,-20} {2}",
item.Year, item.Champion, item.Constructor);
}
}
private static void Join()
{
//var racers = from r in Formula1.GetChampions()
// from y in r.Years
// where y > 2003
// select new { Year = y, Name = r.FirstName + " " + r.LastName };
//var teams = from t in Formula1.GetContructorChampions()
// from y in t.Years
// where y > 2003
// select new { Year = y, Name = t.Name };
//var racersAndTeams = from r in racers
// join t in teams on r.Year equals t.Year
// select new { Year = r.Year, Racer = r.Name, Team = t.Name };
int year = 2003;
var racersAndTeams = from r in
from r1 in Formula1.GetChampions()
from yr in r1.Years
where yr > year
select new { Year = yr, Name = r1.FirstName + " " + r1.LastName }
join t in
from t1 in Formula1.GetContructorChampions()
from yt in t1.Years
where yt > year
select new { Year = yt, Name = t1.Name }
on r.Year equals t.Year
select new { Year = r.Year, Racer = r.Name, Team = t.Name };
Console.WriteLine("Year Champion Constructor Title");
foreach (var item in racersAndTeams)
{
Console.WriteLine("{0}: {1,-20} {2}", item.Year, item.Racer, item.Team);
}
}