Question

我在下表中有一对多关系

产品 [ProductId，Name（varchar）]

关键字 [KeywordId，关键字（varchar）]

KeywordsToProducts [Id，ProductId，KeywordId]

假设搜索文本是“blue pro”。我需要使用operator'和'搜索这两个关键字。如果我执行以下操作：

string test="blue pro";
string[]words = test.Split(new char[] { ' ' }, StringSplitOptions.RemoveEmptyEntries);

var query = from p in Products 

join kp in KeywordsToProducts on p.ProductId equals kp.ProductId 

join kw in Keywords on kp.KeywordId equals kw.KeywordId 

where (words.All(x=>kw.Keyword.Contains(x)))

然后我没有任何说法，因为字段关键字只包含一个单词。

我如何加入'Keywrods.Keyword'db字段记录以便使用'and'运算符进行搜索？

Answer 1

如果您将每个匹配的KeywordsToProducts加入Keywords，您可以收集它们并进行比较：

var query = from p in Products
            join kp in KeywordsToProducts on p.ProductId equals kp.ProductId into kpj
            let kws = (from kp in kpj join kw in Keywords on kp.KeywordId equals kw.KeywordId select kw.Keyword)
            where words.All(w => kws.Any(kw => kw.Contains(w)))
            select p;

但是，如果您单独执行KeywordsToProducts到Keywords join并且首先（请注意它显示连接表将会更好），我认为它更容易理解（并且可能更有效）已被更好地命名为KeywordIdsToProductIds）：

var kwToProducts = from kp in KeywordsToProducts
                   join kw in Keywords on kp.KeywordId equals kw.KeywordId
                   select new { kp.ProductId, kw.Keyword };

var query = from p in Products
            join kwp in kwToProducts on p.ProductId equals kwp.ProductId into kwpj
            where words.All(w => kwpj.Any(kwp => kwp.Keyword.Contains(w)))
            select p;

虽然我（不一定）不喜欢提及它，但请注意EF导航属性可以隐藏连接表并使这个查询更容易。

这将是：

var query = from p in Products
            where words.All(w => p.Keywords.Any(k => k.Contains(w)))
            select p;

我假设您打算使用String.Contains，以便用户可以输入部分关键字并仍然可以找到匹配项。如果您想要匹配所有关键字，请使用相同的代码：

var query = from p in Products
            join kp in KeywordsToProducts on p.ProductId equals kp.ProductId into kpj
            let kws = (from kp in kpj join kw in Keywords on kp.KeywordId equals kw.KeywordId select kw.Keyword)
            where words.All(w => kws.Contains(w))
            select p;

拆分子连接：

var kwToProducts = from kp in KeywordsToProducts
                   join kw in Keywords on kp.KeywordId equals kw.KeywordId
                   select new { kp.ProductId, kw.Keyword };

var query = from p in Products
            join kwp in kwToProducts on p.ProductId equals kwp.ProductId into kwpj
            where words.All(w => kwpj.Select(kwp => kwp.Keyword).Contains(w))
            select p;

EF导航属性：

var query = from p in Products
            where words.All(w => p.Keywords.Contains(w))
            select p;

Linq使用'和'运算符搜索文本

1 个答案: