将 SQL 查询转换为等效的 LINQ
Convert SQL query to equivalent LINQ
SELECT
*
FROM
T_Fighters
LEFT OUTER JOIN T_FighterEnlistments ON
(T_FighterEnlistments.FighterId = T_Fighters.FighterId)
LEFT OUTER JOIN T_FighterTransfers ON
(T_FighterTransfers.FighterId = T_Fighters.FighterId)
LEFT OUTER JOIN T_Battalions ON
(T_Battalions.BattalionId = T_FighterEnlistments.BattalionId OR T_Battalions.BattalionId = T_FighterTransfers.BattalionId)
LEFT OUTER JOIN T_BattalionSideServed ON
(T_BattalionSideServed.BattalionSideServedId = T_Battalions.BattalionSideServedId)
具体低于条件
LEFT OUTER JOIN T_Battalions ON
(T_Battalions.BattalionId = T_FighterEnlistments.BattalionId OR T_Battalions.BattalionId = T_FighterTransfers.BattalionId)
我知道剩下的部分只是不确定上面的左连接或条件。
from fighter in T_Fighters
join fighterEnlistment in T_FighterEnlistments on fighter.FighterId equals fighterEnlistment.FighterId into fighterEnlistments
from subFighterEnlistments in fighterEnlistments.Where(x => !x.WolfError).DefaultIfEmpty()
join soldierTransfer in T_FighterTransfers on fighter.FighterId equals soldierTransfer.FighterId into soldierTransfers
from subsoldierTransfers in soldierTransfers.Where(x=>!x.WolfError).DefaultIfEmpty()
join battalions in T_Battalions on subsoldierTransfers.BattalionId equals battalions.BattalionId into battalions
from subbattalions in battalions.DefaultIfEmpty()
join battalionsSideServed in T_RegimentSideServeds on subbattalions.RegimentSideServedId equals battalionsSideServed.RegimentSideServedId into battalionsSideServeds
from subbattalionsSideServeds in battalionsSideServeds.DefaultIfEmpty()
你快到了。缺少的是使用 Any 作为您独特的左连接或连接集：
- 注意：原来的 SQL 查询似乎与您建议的 Linq 查询不同。一方面，SQL 查询使用
BattalionId，而 Linq 查询使用 RegimentId。其次，Linq 查询使用 SQL 查询中不存在的过滤器（在 WolfError 上）。我建议的查询是指原始 SQL 查询字段，带有附加过滤器。
代码：
from fighter in T_Fighters
join fighterEnlistment in T_FighterEnlistments
on fighter.FighterId equals fighterEnlistment.FighterId into fighterEnlistments
from subFighterEnlistments in fighterEnlistments.Where(x => !x.WolfError).DefaultIfEmpty()
join fighterTransfer in T_FighterTransfers
on fighter.FighterId equals fighterTransfer.FighterId into fighterTransfers
from subFighterTransfers in fighterTransfers.Where(x=>!x.WolfError).DefaultIfEmpty()
from t_battalion in T_Battalions
.Where(battalion => subFighterEnlistments.Any(x => x.BattalionId == battalion.BattalionId) ||
subsoldierTransfers.Any(x => x.BattalionId == battalion.BattalionId))
.DefaultIfEmpty()
join battalionsSideServed in T_BattalionSideServed
on t_battalion.BattalionSideServedId equals battalionsSideServed.BattalionSideServedId into battalionsSideServeds
from subbattalionsSideServeds in battalionsSideServeds.DefaultIfEmpty()
select { ... something ... }
现在，由于在没有一些具体对象的情况下很难理解这一点，下面是在 LinqPad 中完成的上述代码的简化：
void Main()
{
var a = new [] { new A { Id = "A1", Name = "A1" }, new A { Id = "A2", Name = "A2" } };
var b = new [] { new B { Id = "B1", Name = "B1" }, new B { Id = "B2", Name = "B2" } };
var a1b2 = new Base[] { new A { Id = "A1", Name = "A1" }, new B { Id = "B2", Name = "B2" } };
var b1a2 = new Base[] { new B { Id = "B1", Name = "B1" }, new A { Id = "A2", Name = "A2" } };
var a_nulls1 = new [] { new A { Id = "A1", Name = null }, new A { Id = null, Name = "A2" } };
var a_nulls2 = new [] { new B { Id = null, Name = "A1" }, new B { Id = "A2", Name = null } };
var res =
from item_a in a
join item_b in b on item_a.Id equals item_b.Id into joined_ab
from item_joined_ab in joined_ab.DefaultIfEmpty()
join item_a1b2 in a1b2 on item_a.Id equals item_a1b2.Id into joined_a_a1b2
from item_joined_a_a1b2 in joined_a_a1b2.DefaultIfEmpty()
join item_b1a2 in b1a2 on item_a.Id equals item_b1a2.Id into joined_a_b1a2
from item_joined_a_b1a2 in joined_a_b1a2.DefaultIfEmpty()
from item_joined_a1_nulls in a_nulls1
.Where(a_n => joined_a_a1b2.Any(x => x.Id == a_n.Id) ||
joined_a_b1a2.Any(x => x.Name == a_n.Name))
.DefaultIfEmpty()
join item_a2_nulls in a_nulls2 on item_joined_a1_nulls.Id equals item_a2_nulls.Id into joined_a_nulls
from item_joined_a_nulls in joined_a_nulls.DefaultIfEmpty()
select new { item_joined_ab, item_joined_a_a1b2, item_joined_a_b1a2, item_joined_a1_nulls, item_joined_a_nulls };
res.Dump();
}
class Base
{
public string Id { get; set; }
public string Name { get; set; }
}
class A : Base {}
class B : Base {}
结果（只是运行而已，忽略html+css）：
body{margin:0.3em 0.3em 0.4em 0.4em;font-family:Verdana;font-size:80%;background:white}p,pre{margin:0;padding:0;font-family:Verdana}table{border-collapse:collapse;border:2px solid #17b;margin:0.3em 0.2em}table.limit{border-bottom-color:#c31}table.expandable{border-bottom-style:dashed}table.error{border-bottom-width:4px}td,th{vertical-align:top;border:1px solid #aaa;padding:0.1em 0.2em;margin:0}th{text-align:left;background-color:#ddd;border:1px solid #777;font-family:tahoma;font-size:.9em;font-weight:bold}th.member{padding:0.1em 0.2em 0.1em 0.2em}td.typeheader{font-family:tahoma;font-weight:bold;background-color:#17b;color:white;padding:0 0.2em 0.15em 0.1em}td.n{text-align:right}a:link.typeheader,a:visited.typeheader,a:link.extenser,a:visited.extenser,a:link.fixedextenser,a:visited.fixedextenser{font-family:tahoma;font-size:.9em;font-weight:bold;text-decoration:none;background-color:#17b;color:white;float:left}a:link.difheader,a:visited.difheader{color:#ff8}a:link.extenser,a:visited.extenser,a:link.fixedextenser,a:visited.fixedextenser{float:right;padding-left:2pt;margin-left:4pt}span.typeglyph,span.typeglyphx{padding:0 0.2em 0 0;margin:0}span.extenser,span.extenserx,span.fixedextenser{margin-top:1.2pt}span.typeglyph,span.extenser,span.fixedextenser{font-family:webdings}span.fixedextenser{display:none;position:fixed;right:6px}td.typeheader:hover .fixedextenser{display:block}span.typeglyphx,span.extenserx{font-family:arial;font-weight:bold;margin:2px}table.group{border:none;margin:0}td.group{border:none;padding:0 0.1em}div.spacer{margin:0.6em 0}table.headingpresenter{border:none;border-left:3px dotted #1a5;margin:.8em 0 1em 0.15em}th.headingpresenter{font-family:Arial;border:none;padding:0 0 0.2em 0.5em;background-color:white;color:green;font-size:1.1em}td.headingpresenter{border:none;padding:0 0 0 0.6em}td.summary{background-color:#def;color:#024;font-family:Tahoma;padding:0 0.1em 0.1em 0.1em}td.columntotal{font-family:Tahoma;background-color:#eee;font-weight:bold;color:#17b;font-size:.9em;text-align:right}span.graphbar{background:#17b;color:#17b;margin-left:-2px;margin-right:-2px}a:link.graphcolumn,a:visited.graphcolumn{color:#17b;text-decoration:none;font-weight:bold;font-family:Arial;font-size:1.1em;letter-spacing:-0.2em;margin-left:0.1em;margin-right:0.2em}a:link.collection,a:visited.collection{color:green}a:link.reference,a:visited.reference{color:blue}i{color:green}em{color:red}.highlight{background:#ff8}.fixedfont{font-family:Consolas,monospace}code{font-family:Consolas}code.xml b{color:blue;font-weight:normal}code.xml i{color:maroon;font-weight:normal;font-style:normal}code.xml em{color:red;font-weight:normal;font-style:normal}span.cc{background:#666;color:white;margin:0 1.5px;padding:0 1px;font-family:Consolas,monospace;border-radius:3px}.difadd{background:#d3f3d3}.difremove{background:#f3d8d8}::-ms-clear{display:none}input,textarea,button,select{font-family:Verdana;font-size:1em;padding:.2em}button{padding:.2em .4em}input,textarea,select{margin:.15em 0}input[type="checkbox"],input[type="radio"]{margin:0 0.4em 0 0;height:0.9em;width:0.9em}input[type="radio"]:focus,input[type="checkbox"]:focus{outline:thin dotted red}.checkbox-label{vertical-align:middle;position:relative;bottom:.07em;margin-right:.5em}fieldset{margin:0 .2em .4em .1em;border:1pt solid #aaa;padding:.1em .6em .4em .6em}legend{padding:.2em .1em}
<div class="spacer"><table id="t1"><tr><td class="typeheader" colspan="5">(2 items)<span class="fixedextenser">4</span></td></tr><tr><th title="UserQuery+B">item_joined_ab</th><th title="UserQuery+Base">item_joined_a_a1b2</th><th title="UserQuery+Base">item_joined_a_b1a2</th><th title="UserQuery+A">item_joined_a1_nulls</th><th title="UserQuery+B">item_joined_a_nulls</th></tr><tr><td><i>null</i></td><td><table id="t2"><tr><td class="typeheader" colspan="2">A<span class="fixedextenser">4</span></td></tr><tr id="sum3"><td colspan="2" class="summary">UserQuery+A</td></tr><tr><th class="member" title="System.String">Id</th><td>A1</td></tr><tr><th class="member" title="System.String">Name</th><td>A1</td></tr></table></td><td><i>null</i></td><td><table id="t4"><tr><td class="typeheader" colspan="2">A<span class="fixedextenser">4</span></td></tr><tr id="sum5"><td colspan="2" class="summary">UserQuery+A</td></tr><tr><th class="member" title="System.String">Id</th><td>A1</td></tr><tr><th class="member" title="System.String">Name</th><td><i>null</i></td></tr></table></td><td><i>null</i></td></tr><tr><td><i>null</i></td><td><i>null</i></td><td><table id="t6"><tr><td class="typeheader" colspan="2">A<span class="fixedextenser">4</span></td></tr><tr id="sum7"><td colspan="2" class="summary">UserQuery+A</td></tr><tr><th class="member" title="System.String">Id</th><td>A2</td></tr><tr><th class="member" title="System.String">Name</th><td>A2</td></tr></table></td><td><table id="t8"><tr><td class="typeheader" colspan="2">A<span class="fixedextenser">4</span></td></tr><tr id="sum9"><td colspan="2" class="summary">UserQuery+A</td></tr><tr><th class="member" title="System.String">Id</th><td><i>null</i></td></tr><tr><th class="member" title="System.String">Name</th><td>A2</td></tr></table></td><td><i>null</i></td></tr></table></div>
（当然，如果我们将最后一个连接中的 Id 之一改为 Name，我们将得到一个 B 包含在最后一列）。
SELECT
*
FROM
T_Fighters
LEFT OUTER JOIN T_FighterEnlistments ON
(T_FighterEnlistments.FighterId = T_Fighters.FighterId)
LEFT OUTER JOIN T_FighterTransfers ON
(T_FighterTransfers.FighterId = T_Fighters.FighterId)
LEFT OUTER JOIN T_Battalions ON
(T_Battalions.BattalionId = T_FighterEnlistments.BattalionId OR T_Battalions.BattalionId = T_FighterTransfers.BattalionId)
LEFT OUTER JOIN T_BattalionSideServed ON
(T_BattalionSideServed.BattalionSideServedId = T_Battalions.BattalionSideServedId)
具体低于条件
LEFT OUTER JOIN T_Battalions ON (T_Battalions.BattalionId = T_FighterEnlistments.BattalionId OR T_Battalions.BattalionId = T_FighterTransfers.BattalionId)
我知道剩下的部分只是不确定上面的左连接或条件。
from fighter in T_Fighters
join fighterEnlistment in T_FighterEnlistments on fighter.FighterId equals fighterEnlistment.FighterId into fighterEnlistments
from subFighterEnlistments in fighterEnlistments.Where(x => !x.WolfError).DefaultIfEmpty()
join soldierTransfer in T_FighterTransfers on fighter.FighterId equals soldierTransfer.FighterId into soldierTransfers
from subsoldierTransfers in soldierTransfers.Where(x=>!x.WolfError).DefaultIfEmpty()
join battalions in T_Battalions on subsoldierTransfers.BattalionId equals battalions.BattalionId into battalions
from subbattalions in battalions.DefaultIfEmpty()
join battalionsSideServed in T_RegimentSideServeds on subbattalions.RegimentSideServedId equals battalionsSideServed.RegimentSideServedId into battalionsSideServeds
from subbattalionsSideServeds in battalionsSideServeds.DefaultIfEmpty()
你快到了。缺少的是使用 Any 作为您独特的左连接或连接集：
- 注意：原来的 SQL 查询似乎与您建议的 Linq 查询不同。一方面，SQL 查询使用
BattalionId，而 Linq 查询使用RegimentId。其次，Linq 查询使用 SQL 查询中不存在的过滤器（在WolfError上）。我建议的查询是指原始 SQL 查询字段，带有附加过滤器。
代码：
from fighter in T_Fighters
join fighterEnlistment in T_FighterEnlistments
on fighter.FighterId equals fighterEnlistment.FighterId into fighterEnlistments
from subFighterEnlistments in fighterEnlistments.Where(x => !x.WolfError).DefaultIfEmpty()
join fighterTransfer in T_FighterTransfers
on fighter.FighterId equals fighterTransfer.FighterId into fighterTransfers
from subFighterTransfers in fighterTransfers.Where(x=>!x.WolfError).DefaultIfEmpty()
from t_battalion in T_Battalions
.Where(battalion => subFighterEnlistments.Any(x => x.BattalionId == battalion.BattalionId) ||
subsoldierTransfers.Any(x => x.BattalionId == battalion.BattalionId))
.DefaultIfEmpty()
join battalionsSideServed in T_BattalionSideServed
on t_battalion.BattalionSideServedId equals battalionsSideServed.BattalionSideServedId into battalionsSideServeds
from subbattalionsSideServeds in battalionsSideServeds.DefaultIfEmpty()
select { ... something ... }
现在，由于在没有一些具体对象的情况下很难理解这一点，下面是在 LinqPad 中完成的上述代码的简化：
void Main()
{
var a = new [] { new A { Id = "A1", Name = "A1" }, new A { Id = "A2", Name = "A2" } };
var b = new [] { new B { Id = "B1", Name = "B1" }, new B { Id = "B2", Name = "B2" } };
var a1b2 = new Base[] { new A { Id = "A1", Name = "A1" }, new B { Id = "B2", Name = "B2" } };
var b1a2 = new Base[] { new B { Id = "B1", Name = "B1" }, new A { Id = "A2", Name = "A2" } };
var a_nulls1 = new [] { new A { Id = "A1", Name = null }, new A { Id = null, Name = "A2" } };
var a_nulls2 = new [] { new B { Id = null, Name = "A1" }, new B { Id = "A2", Name = null } };
var res =
from item_a in a
join item_b in b on item_a.Id equals item_b.Id into joined_ab
from item_joined_ab in joined_ab.DefaultIfEmpty()
join item_a1b2 in a1b2 on item_a.Id equals item_a1b2.Id into joined_a_a1b2
from item_joined_a_a1b2 in joined_a_a1b2.DefaultIfEmpty()
join item_b1a2 in b1a2 on item_a.Id equals item_b1a2.Id into joined_a_b1a2
from item_joined_a_b1a2 in joined_a_b1a2.DefaultIfEmpty()
from item_joined_a1_nulls in a_nulls1
.Where(a_n => joined_a_a1b2.Any(x => x.Id == a_n.Id) ||
joined_a_b1a2.Any(x => x.Name == a_n.Name))
.DefaultIfEmpty()
join item_a2_nulls in a_nulls2 on item_joined_a1_nulls.Id equals item_a2_nulls.Id into joined_a_nulls
from item_joined_a_nulls in joined_a_nulls.DefaultIfEmpty()
select new { item_joined_ab, item_joined_a_a1b2, item_joined_a_b1a2, item_joined_a1_nulls, item_joined_a_nulls };
res.Dump();
}
class Base
{
public string Id { get; set; }
public string Name { get; set; }
}
class A : Base {}
class B : Base {}
结果（只是运行而已，忽略html+css）：
body{margin:0.3em 0.3em 0.4em 0.4em;font-family:Verdana;font-size:80%;background:white}p,pre{margin:0;padding:0;font-family:Verdana}table{border-collapse:collapse;border:2px solid #17b;margin:0.3em 0.2em}table.limit{border-bottom-color:#c31}table.expandable{border-bottom-style:dashed}table.error{border-bottom-width:4px}td,th{vertical-align:top;border:1px solid #aaa;padding:0.1em 0.2em;margin:0}th{text-align:left;background-color:#ddd;border:1px solid #777;font-family:tahoma;font-size:.9em;font-weight:bold}th.member{padding:0.1em 0.2em 0.1em 0.2em}td.typeheader{font-family:tahoma;font-weight:bold;background-color:#17b;color:white;padding:0 0.2em 0.15em 0.1em}td.n{text-align:right}a:link.typeheader,a:visited.typeheader,a:link.extenser,a:visited.extenser,a:link.fixedextenser,a:visited.fixedextenser{font-family:tahoma;font-size:.9em;font-weight:bold;text-decoration:none;background-color:#17b;color:white;float:left}a:link.difheader,a:visited.difheader{color:#ff8}a:link.extenser,a:visited.extenser,a:link.fixedextenser,a:visited.fixedextenser{float:right;padding-left:2pt;margin-left:4pt}span.typeglyph,span.typeglyphx{padding:0 0.2em 0 0;margin:0}span.extenser,span.extenserx,span.fixedextenser{margin-top:1.2pt}span.typeglyph,span.extenser,span.fixedextenser{font-family:webdings}span.fixedextenser{display:none;position:fixed;right:6px}td.typeheader:hover .fixedextenser{display:block}span.typeglyphx,span.extenserx{font-family:arial;font-weight:bold;margin:2px}table.group{border:none;margin:0}td.group{border:none;padding:0 0.1em}div.spacer{margin:0.6em 0}table.headingpresenter{border:none;border-left:3px dotted #1a5;margin:.8em 0 1em 0.15em}th.headingpresenter{font-family:Arial;border:none;padding:0 0 0.2em 0.5em;background-color:white;color:green;font-size:1.1em}td.headingpresenter{border:none;padding:0 0 0 0.6em}td.summary{background-color:#def;color:#024;font-family:Tahoma;padding:0 0.1em 0.1em 0.1em}td.columntotal{font-family:Tahoma;background-color:#eee;font-weight:bold;color:#17b;font-size:.9em;text-align:right}span.graphbar{background:#17b;color:#17b;margin-left:-2px;margin-right:-2px}a:link.graphcolumn,a:visited.graphcolumn{color:#17b;text-decoration:none;font-weight:bold;font-family:Arial;font-size:1.1em;letter-spacing:-0.2em;margin-left:0.1em;margin-right:0.2em}a:link.collection,a:visited.collection{color:green}a:link.reference,a:visited.reference{color:blue}i{color:green}em{color:red}.highlight{background:#ff8}.fixedfont{font-family:Consolas,monospace}code{font-family:Consolas}code.xml b{color:blue;font-weight:normal}code.xml i{color:maroon;font-weight:normal;font-style:normal}code.xml em{color:red;font-weight:normal;font-style:normal}span.cc{background:#666;color:white;margin:0 1.5px;padding:0 1px;font-family:Consolas,monospace;border-radius:3px}.difadd{background:#d3f3d3}.difremove{background:#f3d8d8}::-ms-clear{display:none}input,textarea,button,select{font-family:Verdana;font-size:1em;padding:.2em}button{padding:.2em .4em}input,textarea,select{margin:.15em 0}input[type="checkbox"],input[type="radio"]{margin:0 0.4em 0 0;height:0.9em;width:0.9em}input[type="radio"]:focus,input[type="checkbox"]:focus{outline:thin dotted red}.checkbox-label{vertical-align:middle;position:relative;bottom:.07em;margin-right:.5em}fieldset{margin:0 .2em .4em .1em;border:1pt solid #aaa;padding:.1em .6em .4em .6em}legend{padding:.2em .1em}
<div class="spacer"><table id="t1"><tr><td class="typeheader" colspan="5">(2 items)<span class="fixedextenser">4</span></td></tr><tr><th title="UserQuery+B">item_joined_ab</th><th title="UserQuery+Base">item_joined_a_a1b2</th><th title="UserQuery+Base">item_joined_a_b1a2</th><th title="UserQuery+A">item_joined_a1_nulls</th><th title="UserQuery+B">item_joined_a_nulls</th></tr><tr><td><i>null</i></td><td><table id="t2"><tr><td class="typeheader" colspan="2">A<span class="fixedextenser">4</span></td></tr><tr id="sum3"><td colspan="2" class="summary">UserQuery+A</td></tr><tr><th class="member" title="System.String">Id</th><td>A1</td></tr><tr><th class="member" title="System.String">Name</th><td>A1</td></tr></table></td><td><i>null</i></td><td><table id="t4"><tr><td class="typeheader" colspan="2">A<span class="fixedextenser">4</span></td></tr><tr id="sum5"><td colspan="2" class="summary">UserQuery+A</td></tr><tr><th class="member" title="System.String">Id</th><td>A1</td></tr><tr><th class="member" title="System.String">Name</th><td><i>null</i></td></tr></table></td><td><i>null</i></td></tr><tr><td><i>null</i></td><td><i>null</i></td><td><table id="t6"><tr><td class="typeheader" colspan="2">A<span class="fixedextenser">4</span></td></tr><tr id="sum7"><td colspan="2" class="summary">UserQuery+A</td></tr><tr><th class="member" title="System.String">Id</th><td>A2</td></tr><tr><th class="member" title="System.String">Name</th><td>A2</td></tr></table></td><td><table id="t8"><tr><td class="typeheader" colspan="2">A<span class="fixedextenser">4</span></td></tr><tr id="sum9"><td colspan="2" class="summary">UserQuery+A</td></tr><tr><th class="member" title="System.String">Id</th><td><i>null</i></td></tr><tr><th class="member" title="System.String">Name</th><td>A2</td></tr></table></td><td><i>null</i></td></tr></table></div>
（当然，如果我们将最后一个连接中的 Id 之一改为 Name，我们将得到一个 B 包含在最后一列）。