我是linq的新手,想要在三个表中执行连接。我试图做的sql相当于:
SELECT PM.Id, PM.new_clientId, .....
C.new_firstname, c.new_surname,.....
A.new_addressid, A.new_addressline1, A.new_addressline2.....
CY.new_county
FROM partialMatch PM
INNER JOIN new_client C ON PM.new_clientId = C.new_clientId
LEFT OUTER JOIN new_address A ON C.new_addressId = A.new_addressId
LEFT OUTER JOIN new_county CY ON A.new_countyId = CY.new_countyId
WHERE PM.ownerId = @UserId AND PM.new_reviewed <> true
我开发的linq代码是这样的,但是这些似乎不是外连接,因为它没有返回任何结果,除非我注释掉地址和县表的连接
var partialMatches = from pm in ContextService.CreateQuery<new_partialmatch>()
join c in ContextService.CreateQuery<new_client>() on pm.new_ClientId.Id equals c.new_clientId
join a in ContextService.CreateQuery<new_address>() on c.new_AddressID.Id equals a.new_addressId
join cy in ContextService.CreateQuery<new_county>() on a.new_CountyID.Id equals cy.new_countyId
where pm.OwnerId.Id == _currentUserId && pm.new_Reviewed != true
select new
{
Id = pm.Id,
new_ClientID = pm.new_ClientId,
new_MatchingCRMClientID = pm.new_MatchingCRMClientId,
new_MatchingVulcanClientID = pm.new_MatchingVulcanClientID,
new_name = pm.new_name,
firstname = c.new_FirstName,
surname = c.new_Surname,
dob = c.new_DateOfBirth,
addressId = a.new_addressId,
address1 = a.new_AddressLine1,
address2 = a.new_AddressLine2,
address3 = a.new_AddressLine3,
address4 = a.new_AddressLine4,
county = cy.new_County
};
非常感谢任何帮助,
谢谢, 尼尔
编辑:
我也尝试使用'into'语句,但是在我的第二次加入时,别名无法识别。
from pm in ContextService.CreateQuery<new_partialmatch>()
join c in ContextService.CreateQuery<new_client>() on pm.new_ClientId.Id equals c.new_clientId into pmc
from x in pmc.DefaultIfEmpty()
join a in ContextService.CreateQuery<new_address>() on c.new_AddressID.Id equals a.new_addressId
因此,对于c.newIddressID.Id等于a.new_addressId,我收到此错误消息:
名称'c'不在'equals'左侧的范围内。考虑交换'equals'两侧的表达式。
答案 0 :(得分:1)
var addressCountryQuery = from a in ContextService.CreateQuery<new_address>()
from cy in ContextService.CreateQuery<new_county>().Where( cy => cy.new_countyId == a.new_CountyID.Id).DefaultIfEmpty()
select new
{
addressId = a.new_addressId,
address1 = a.new_AddressLine1,
address2 = a.new_AddressLine2,
address3 = a.new_AddressLine3,
address4 = a.new_AddressLine4,
county = cy.new_County
}
var partialMatches = from pm in ContextService.CreateQuery<new_partialmatch>()
join c in ContextService.CreateQuery<new_client>() on pm.new_ClientId.Id equals c.new_clientId
from a in addressCountryQuery .Where( a => a.addressId == c.new_AddressID.Id).DefaultIfEmpty()
where pm.OwnerId.Id == _currentUserId && pm.new_Reviewed != true
select new
{
Id = pm.Id,
new_ClientID = pm.new_ClientId,
new_MatchingCRMClientID = pm.new_MatchingCRMClientId,
new_MatchingVulcanClientID = pm.new_MatchingVulcanClientID,
new_name = pm.new_name,
firstname = c.new_FirstName,
surname = c.new_Surname,
dob = c.new_DateOfBirth,
addressId = a.addressId,
address1 = a.AddressLine1,
address2 = a.AddressLine2,
address3 = a.AddressLine3,
address4 = a.AddressLine4,
county = a.County
};
看看我是如何修改a和cy的连接所以我可以添加DefultIfEmpty方法。
我将两个外部联接分成一个查询,然后将该查询加回到原始查询中。