Linq 多个左连接 怎么写？ ##################################

[t101lian]

select a.* ,c.Class_name from 
( 
select a.NickName,b.*  from UserTb a 
 left join SpecialTreatmentTb  b  on a.userid=b.userid 
) a

left join  GoodsTb c on a.goodid=c.id

请教各位大侠，
这句SQL ，用Linq 怎么写？
回复后再加分！

[-烟花雨季]

var lowNums =
            (from a in SpecialTreatmentInfoLsit
            join b in uInfoList on a.UserId equals b.UserId
            into c
            from d in c.DefaultIfEmpty()
            join x in GinfoList on a.GoodId equals x.ID
            into y
            from endStords in y.DefaultIfEmpty()
            select new
            {
                d.UserId,
                d.NickName,
                d.Address,
                FeeRate = endStords == null ? 0 : endStords.FeeRate,
                BailRate = endStords == null ? 0 : endStords.BailRate,
                SellBailRate = endStords == null ? 0 : endStords.SellBailRate,
                SellFeeRate = endStords == null ? 0 : endStords.SellFeeRate
            });

[threenewbee]

写法和sql类似，先前两个连接，再连接第三个即可。

[-烟花雨季]

var lowNums =
            (from a in SpecialTreatmentTb
             join b in UserTb on a.userid equals b.userid
             into c
             from d in c.DefaultIfEmpty()
             join x in GoodsTb on a.id equals x.goodid
             into y
             from z in y.DefaultIfEmpty()
             select new
             {
                 d.NickName,
                 z.Class_name,
                 a.xx//(SpecialTreatmentTb以下查这个表里面的数据)
             });

[t101lian]

引用 3 楼 u010349035 的回复:

var lowNums =
            (from a in SpecialTreatmentTb
             join b in UserTb on a.userid equals b.userid
             into c
             from d in c.DefaultIfEmpty()
             join x in GoodsTb on a.id equals x.goodid
             into y
             from z in y.DefaultIfEmpty()
             select new
             {
                 d.NickName,
                 z.Class_name,
                 a.xx//(SpecialTreatmentTb以下查这个表里面的数据)
             });

引用 2 楼 caozhy 的回复:

写法和sql类似，先前两个连接，再连接第三个即可。

语法没错误， 不过查不到数据， 调试发现 存在null ， 是怎么回事？

[-烟花雨季]

引用 4 楼 t101lian 的回复:

[quote=引用 3 楼 u010349035 的回复:]

var lowNums =
            (from a in SpecialTreatmentTb
             join b in UserTb on a.userid equals b.userid
             into c
             from d in c.DefaultIfEmpty()
             join x in GoodsTb on a.id equals x.goodid
             into y
             from z in y.DefaultIfEmpty()
             select new
             {
                 d.NickName,
                 z.Class_name,
                 a.xx//(SpecialTreatmentTb以下查这个表里面的数据)
             });

引用 2 楼 caozhy 的回复:

写法和sql类似，先前两个连接，再连接第三个即可。

语法没错误， 不过查不到数据， 调试发现 存在null ， 是怎么回事？ [/quote] 表里面有数据为null的判断一下

[t101lian]

引用 5 楼 u010349035 的回复:

[quote=引用 4 楼 t101lian 的回复:] [quote=引用 3 楼 u010349035 的回复:]

var lowNums =
            (from a in SpecialTreatmentTb
             join b in UserTb on a.userid equals b.userid
             into c
             from d in c.DefaultIfEmpty()
             join x in GoodsTb on a.id equals x.goodid
             into y
             from z in y.DefaultIfEmpty()
             select new
             {
                 d.NickName,
                 z.Class_name,
                 a.xx//(SpecialTreatmentTb以下查这个表里面的数据)
             });

引用 2 楼 caozhy 的回复:

写法和sql类似，先前两个连接，再连接第三个即可。

语法没错误， 不过查不到数据， 调试发现 存在null ， 是怎么回事？ [/quote] 表里面有数据为null的判断一下[/quote]

  var lowNums =
                from a in SpecialTreatmentInfoLsit
                join b in uInfoList on a.UserId equals b.UserId 
                into c 
                from d in c.DefaultIfEmpty()

                join x in GinfoList on a.GoodId equals x.ID.ToString()
                into y
                from z in y.DefaultIfEmpty()

            select new
            {
                d.UserId,
                d.NickName,
                d.Address,
                ClassName =z==null?"": z.Class_Name,
                FeeRate = a == null ? 0 : a.FeeRate,
                BailRate = a == null ? 0 : a.BailRate,
                SellBailRate = a == null ? 0 : a.SellBailRate,
                SellFeeRate = a == null ? 0 : a.SellFeeRate,
            };

都判断了， 不过调试还是提示 未引用对象实例化。。。

[-烟花雨季]

ClassName = z.Class_Name == null ? "" : z.Class_Name,
                FeeRate = a.FeeRate == null ? 0 : a.FeeRate,
                BailRate = a.BailRate == null ? 0 : a.BailRate,
                SellBailRate = a.SellBailRate == null ? 0 : a.SellBailRate,
                SellFeeRate = a.SellFeeRate == null ? 0 : a.SellFeeRate,

[t101lian]

引用 3 楼 u010349035 的回复:

var lowNums =
            (from a in SpecialTreatmentTb
             join b in UserTb on a.userid equals b.userid
             into c
             from d in c.DefaultIfEmpty()
             join x in GoodsTb on a.id equals x.goodid
             into y
             from z in y.DefaultIfEmpty()
             select new
             {
                 d.NickName,
                 z.Class_name,
                 a.xx//(SpecialTreatmentTb以下查这个表里面的数据)
             });

改了还是不行， 大神， 你这个是不是把 SpecialTreatmentTb 表当作 左表了？ 我需要把其他两个表作为 左表

select a.* ,c.Class_name from 
( 
select a.NickName,b.*  from UserTb a 
 left join SpecialTreatmentTb  b  on a.userid=b.userid 
) a
 
left join  GoodsTb c on a.goodid=c.id

[-烟花雨季]

这个是主表SpecialTreatmentTb 另外两个是从表，其余两个表都跟SpecialTreatmentTb 这个有关系么

[t101lian]

引用 9 楼 u010349035 的回复:

这个是主表SpecialTreatmentTb 另外两个是从表，其余两个表都跟SpecialTreatmentTb 这个有关系么

上面SQL 语句中 a表才是 主表。

[t101lian]

引用 9 楼 u010349035 的回复:

这个是主表SpecialTreatmentTb 另外两个是从表，其余两个表都跟SpecialTreatmentTb 这个有关系么

大神帮帮看看这个吧 var lowNums = from q in uInfoList join m in ( from s in SpecialTreatmentInfoLsit join g in GinfoList on s.GoodId equals g.ID select s ) on q.UserId equals m.UserId into Stords from endStords in Stords.DefaultIfEmpty() select new { q.UserId, q.NickName, 这里要加上GinfoList中的一个字段怎么写？ （g.name 不行呢） q.Address, FeeRate = endStords == null ? 0 : endStords.FeeRate, BailRate = endStords == null ? 0 : endStords.BailRate, SellBailRate = endStords == null ? 0 : endStords.SellBailRate, SellFeeRate = endStords == null ? 0 : endStords.SellFeeRate, }

[-烟花雨季]

endStords.name

[geyewei]

var lowNums = from q in uInfoList join m in ( from s in SpecialTreatmentInfoLsit join g in GinfoList on s.GoodId equals g.ID select s,g ) on q.UserId equals m.s.UserId into Stords from endStords in Stords.DefaultIfEmpty() select new { q.UserId, q.NickName, name = endStords == null ? "" : endStords.g.name, q.Address, FeeRate = endStords == null ? 0 : endStords.s.FeeRate, BailRate = endStords == null ? 0 : endStords.s.BailRate, SellBailRate = endStords == null ? 0 : endStords.s.SellBailRate, SellFeeRate = endStords == null ? 0 : endStords.s.SellFeeRate, }

[Rajesh_James]

var items = from a in db.UserTb join b in db. SpecialTreatmentTb 
on a.userid equals b.userid select new { a.NickName, b};
var res = from a in items join b in db.GoodsTb  on a.goodid equals b.id select new {a,b.classname};

没有在编译器中跑，只是为了给楼主一个思路，希望对楼主有用

[geyewei]

引用 16 楼 t101lian 的回复:

[quote=引用 13 楼 geyewei 的回复:] var lowNums = from q in uInfoList join m in ( from s in SpecialTreatmentInfoLsit join g in GinfoList on s.GoodId equals g.ID select s,g ) on q.UserId equals m.s.UserId into Stords from endStords in Stords.DefaultIfEmpty() select new { q.UserId, q.NickName, name = endStords == null ? "" : endStords.g.name, q.Address, FeeRate = endStords == null ? 0 : endStords.s.FeeRate, BailRate = endStords == null ? 0 : endStords.s.BailRate, SellBailRate = endStords == null ? 0 : endStords.s.SellBailRate, SellFeeRate = endStords == null ? 0 : endStords.s.SellFeeRate, }

大神帮我再看看， 试过了， 还是不行， 第一处加红的地方就报错了， ,g 不行。 ，[/quote] 哦，那就把select s,g改成select new { s = s, g = g}吧。

[t101lian]

引用 12 楼 u010349035 的回复:

endStords.name

试过，没用的 endStords只有SpecialTreatmentInfoLsit 的字段，

[t101lian]

引用 13 楼 geyewei 的回复:

var lowNums = from q in uInfoList join m in ( from s in SpecialTreatmentInfoLsit join g in GinfoList on s.GoodId equals g.ID select s,g ) on q.UserId equals m.s.UserId into Stords from endStords in Stords.DefaultIfEmpty() select new { q.UserId, q.NickName, name = endStords == null ? "" : endStords.g.name, q.Address, FeeRate = endStords == null ? 0 : endStords.s.FeeRate, BailRate = endStords == null ? 0 : endStords.s.BailRate, SellBailRate = endStords == null ? 0 : endStords.s.SellBailRate, SellFeeRate = endStords == null ? 0 : endStords.s.SellFeeRate, }

大神帮我再看看， 试过了， 还是不行， 第一处加红的地方就报错了， ,g 不行。 ，

[t101lian]

自己顶一下

[t101lian]

引用 18 楼 geyewei 的回复:

[quote=引用 16 楼 t101lian 的回复:] 大神帮我再看看， 试过了， 还是不行， 第一处加红的地方就报错了， ,g 不行。 ，

哦，那就把select s,g改成select new { s = s, g = g}吧。 [/quote] 谢谢大神， ！！