更高级一些的映射,然后在我的previous question :)小巧玲珑的中间映射
表:
create table [Primary] (
Id int not null,
CustomerId int not null,
CustomerName varchar(60) not null,
Date datetime default getdate(),
constraint PK_Primary primary key (Id)
)
create table Secondary(
PrimaryId int not null,
Id int not null,
Date datetime default getdate(),
constraint PK_Secondary primary key (PrimaryId, Id),
constraint FK_Secondary_Primary foreign key (PrimaryId) references [Primary] (Id)
)
create table Tertiary(
PrimaryId int not null,
SecondaryId int not null,
Id int not null,
Date datetime default getdate(),
constraint PK_Tertiary primary key (PrimaryId, SecondaryId, Id),
constraint FK_Tertiary_Secondary foreign key (PrimaryId, SecondaryId) references Secondary (PrimaryId, Id)
)
类:
public class Primary
{
public int Id { get; set; }
public Customer Customer { get; set; }
public DateTime Date { get; set; }
public List<Secondary> Secondaries { get; set; }
}
public class Secondary
{
public int Id { get; set; }
public DateTime Date { get; set; }
public List<Tertiary> Tertiarys { get; set; }
}
public class Tertiary
{
public int Id { get; set; }
public DateTime Date { get; set; }
}
public class Customer
{
public int Id { get; set; }
public string Name { get; set; }
}
是否有可能使用一个选择,以填补他们所有?事情是这样的:
const string sqlStatement = @"
select
p.Id, p.CustomerId, p.CustomerName, p.Date,
s.Id, s.Date,
t.Id, t.Date
from
[Primary] p left join Secondary s on (p.Id = s.PrimaryId)
left join Tertiary t on (s.PrimaryId = t.PrimaryId and s.Id = t.SecondaryId)
order by
p.Id, s.Id, t.Id
";
然后:
IEnumerable<Primary> primaries = connection.Query<Primary, Customer, Secondary, Tertiary, Primary>(
sqlStatement,
... here comes dragons ...
);
EDIT1 - 我可以有两个嵌套循环做到这一点(的foreach次级 - >的foreach第三会)进行,每一项目的查询,但只是想知道如果可以用单个数据库调用完成。
Edit2 - 也许QueryMultiple方法在这里是合适的,但如果我理解正确,那么我需要多个select语句。在我现实生活中的例子中,select有20多个条件(在where子句中),其中搜索参数可能为空,所以我不想重复所有查询中所有那些语句...