Question

SQL请求：

DECLARE @search varchar(20)
set @search = '%a%'

Select distinct top (500) 
    Customer.Number,Contact.name, Address.StreetAddress, Phone.Number, 
    Customer.Type               
from 
    Customer
left join 
    dbo.Address on dbo.Customer.ContactId  = dbo.Address.ContactId
left join 
    dbo.Contact on dbo.Customer.ContactId  = dbo.Contact.Id
left join 
    dbo.Phone on dbo.Customer.ContactId  = dbo.Phone.ContactId 
              and Phone.Sequence = 1
where 
    Customer.IsActive = 1 
    and Customer.ContactId 
        in (--Primary Contact
            SELECT  Customer.ContactId
            FROM dbo.Customer
            INNER JOIN dbo.Contact ON dbo.Contact.id = dbo.Customer.ContactId
            LEFT JOIN dbo.Email ON dbo.Customer.ContactId  = dbo.Email.ContactId
            LEFT JOIN dbo.Phone ON dbo.Customer.ContactId  = dbo.Phone.ContactId
            LEFT JOIN dbo.Address ON dbo.Customer.ContactId  = dbo.Address.ContactId
            WHERE 
                Contact.FirstNameCareOf LIKE @search
                OR Contact.Name LIKE @search
                OR Email.Address LIKE @search
                OR Phone.Number LIKE @search
                OR Address.StreetAddress LIKE @search
                OR Address.City LIKE @search
                OR Address.ZipCode LIKE @search

          union

          --Secondary Contacts
          SELECT Customer.ContactId
          FROM dbo.Customer
          INNER JOIN dbo.Relationship ON dbo.Contact.Id = dbo.Relationship.TargetContactId
          INNER JOIN dbo.Contact on dbo.Contact.id = dbo.Relationship.SourceContactId
          LEFT JOIN dbo.Email ON dbo.Contact.Id = dbo.Email.ContactId
          LEFT JOIN dbo.Phone ON dbo.Contact.Id = dbo.Phone.ContactId
          WHERE 
            Contact.FirstNameCareOf LIKE @search
            OR Contact.Name LIKE @search
            OR Email.Address LIKE @search
            OR Phone.Number LIKE @search)
order by
    Customer.Number

这是我到目前为止所得到的：

from customerTable in Customers

    join contactTable in Contacts
        on customerTable.ContactId equals contactTable.Id

    join addressTable in Addresses
        on customerTable.ContactId equals addressTable.ContactId

    // the following may no exists for the customer so we dont want to join them since the customer will not be in the request results because of this  
    //  join phoneTable in Phones
    //      on customerTable.ContactId equals phoneTable.ContactId 
    //      
    //  join emailTable in Emails
    //      on customerTable.ContactId equals emailTable.ContactId

    // alternate method to query email and phone table without effecting the results    
    let emailMatch = Emails.Where (p => p.ContactId == customerTable.ContactId && p.Address.Contains("a"))
    let phoneMatch = Phones.Where (p => p.ContactId == customerTable.ContactId && p.Number.Contains("a"))

    where customerTable.IsActive && ( contactTable.Name.Contains("a") || contactTable.FirstNameCareOf.Contains("a") ||addressTable.StreetAddress.Contains("a") || addressTable.City.Contains("a") ||    
                                          addressTable.ZipCode.Contains("a") || emailMatch.Any()|| phoneMatch.Any() )
 orderby customerTable.Number 
            select new {CustomerNumber = customerTable.Number, contactTable.Name, addressTable.StreetAddress, customerTable.Type.EnumId}

问题

有没有一种简单的方法可以将我的SQL请求转换为linq到实体？过了一天，我还在玩上面的linq请求
在我的SQL请求中执行内连接和左连接的真实且最高效的方法是什么？
尝试转换EXACT SQL请求＆＃34;语句＆＃34;是否有意义到linq？或者在linq中使用完全不同的方法更好吗？我的意思是在SQL中执行此操作的最高效方法在linq中根本不一定是相同的方法吗？
当取消注释连接到手机....它不会返回没有手机的任何客户...是否可以返回结果，即使手机桌上没有任何东西可以加入客户？

感谢您提供任何帮助或任何事情。

Answer 1

您的前三个问题的回答是：使用导航属性。出于某种原因，来自SQL背景的人几乎总是开始用join语句编写LINQ。这至少有三个主要缺点：join语句 -

是详细的
没有揭示关联的多样性。声明
```
from customerTable in Customers
join contactTable in Contacts ...
```
未告诉我，客户联系人是1-n，n-1还是1-1。
容易出错：你必须输入连接列，你可以选错了（我已经看过它了。）

如果您使用正确命名的导航属性，例如

，这一切都会发生变化

from cust in Customers
from cont in cust.Contacts ...

它很短，它表明关联是1-n，您只需配置一次关联，而不再关心连接列。

因此，如果您这样做，您的查询将形如

from cust in Customers
where cust.Contacts
          .Any(cont => cont.Name.Contains("a")
                    || cont.FirstNameCareOf.Contains("a")
                    || cont.Address.StreetAddress.Contains("a")
                    || cont.Address.City.Contains("a")
                    || ...  )
   || cust.Relationships
          .Any(rel => rel.TargetContact.Name.Contains("a")
                   || rel.TargetContact.FirstNameCareOf.Contains("a")
                   || rel.TargetContact.Address.StreetAddress.Contains("a")
                   || rel.TargetContact.Address.City.Contains("a")
                   || ...  )
select cust

（如你所见，我必须猜测客户关系的多样性）

这将生成一个SQL查询，其中主谓词由EXIST语句组成。我认为这比IN和DISTINCT的组合更好，因为EXIST是一种有效的搜索策略。

关于您的第四个问题：您还可以在查询中包含电话中的匹配项以及|| cont.Phone == null。

Answer 2

好像你可以使用你正在搜索的4个实体并结合结果..

这是一个非常大的查询，但作为起点，你可以使用。

var contacts = from c in Contacts
               where c.FirstNameCareOf.Contains("c") ||
                     c.Name.Contains("c")
               select c.Customer;

var emails =   from e in Emails
               where e.Address.Contains("c")
               select e.Contact.Customer;

然后当您拥有所有客户时，只需将它们添加到列表中即可。

var customers = new List<Customer>();
customers.AddRange(contacts);
customers.AddRange(emails);
etc..

SQL转换为Linq到实体

2 个答案: