你如何执行交叉参加有皇宫SQL?
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09-06-2019 - |
题
你如何执行交叉参加有皇宫SQL?
解决方案
截加入只是笛卡尔的产品的两套。有没有明确加入操作员用它。
var combo = from p in people from c in cars select new { p.Name, c.Make, c.Model, c.Colour };
其他提示
同样的事情 linq
扩展方法:
var names = new string[] { "Ana", "Raz", "John" };
var numbers = new int[] { 1, 2, 3 };
var newList=names.SelectMany(
x => numbers,
(y, z) => { return y + z + " test "; });
foreach (var item in newList)
{
Console.WriteLine(item);
}
根据史蒂夫是的答案,最简单的表情会是这个:
var combo = from Person in people
from Car in cars
select new {Person, Car};
一个 Tuple
是一个很好的类型为笛卡尔的产品:
public static IEnumerable<Tuple<T1, T2>> CrossJoin<T1, T2>(IEnumerable<T1> sequence1, IEnumerable<T2> sequence2)
{
return sequence1.SelectMany(t1 => sequence2.Select(t2 => Tuple.Create(t1, t2)));
}
扩展的方法:
public static IEnumerable<Tuple<T1, T2>> CrossJoin<T1, T2>(this IEnumerable<T1> sequence1, IEnumerable<T2> sequence2)
{
return sequence1.SelectMany(t1 => sequence2.Select(t2 => Tuple.Create(t1, t2)));
}
和使用,如:
vals1.CrossJoin(vals2)
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