我有以下查询，并希望转换为LINQ。
我尝试过LINQPad和Linqer，但在Visual Studio中出错。
SELECT DISTINCT
g.TXT_Property,
up.TXT_Page
FROM MD g
LEFT JOIN MD ux ON ux.TXT_Page = @sPage
AND ux.TXT_Property = g.TXT_Property
AND ux.TXT_Product = @sProdAll
AND ux.GID_Section IS NULL
LEFT JOIN MD up ON up.TXT_Page = @sPage
AND up.TXT_Property = g.TXT_Property
AND (ISNULL(up.TXT_Product, '') = @sProd or up.TXT_Product = @sProdAlt)
AND up.GID_Section IS NULL
WHERE
(g.GID_Section IS NULL)
AND g.TXT_Page = @sPage
and (ISNULL(g.TXT_Product, '') = @sProd or g.TXT_Product = @sProdAlt or g.TXT_Product = @sProdAll)
ORDER BY TXT_Property, TXT_Product, TXT_Language
这就是我的尝试：
var query2 = from g in list
join ux in list
on g.Property equals ux.Property into g_ux
where ux.Page == sPage
&& ux.Product == sProdAll
&& ux.Section == null
这是另一种尝试。
我提到过 SQL to LINQ - multiple tables left outer join with where clause referring right table
//另一个查询
var query = (from g in
((from d in list
where ((d.Section == null || d.Section == uSection) && (d.Product == sProd || (sProd == "" && d.Product == null) || (d.Product == sProdAlt) || (d.Product == sProdAll)))
select (new { d.Property })).ToList())
join gx in
((from d in list
where (d.Section == null) && (d.Product == sProdAll)
select (new { d.Property, d.Page, d.Product, d.Language, d.Value, d.Section })).ToList())
on g.Property equals gx.Property into res1
from a1 in res1.DefaultIfEmpty()
join gp in
((from d in list
where (d.Section == null) && (d.Product == sProd || (sProd == "" && d.Product == null) || (d.Product == sProdAlt))
select (new { d.Property, d.Page, d.Product, d.Language, d.Value, d.Section })).ToList())
on g.Property equals gp.Property into res2
from a2 in res2.DefaultIfEmpty()
join ux in
((from d in list
where (d.Section == uSection) && (d.Product == sProdAll)
select (new { d.Property, d.Page, d.Product, d.Language, d.Value, d.Section })).ToList())
on g.Property equals ux.Property into res3
from a3 in res3.DefaultIfEmpty()
join up in
((from d in list
where (d.Section == uSection) && (d.Product == sProd || (sProd == "" && d.Product == null) || (d.Product == sProdAlt))
select (new { d.Property, d.Page, d.Product, d.Language, d.Value, d.Section })).ToList())
on g.Property equals up.Property into res4
from a4 in res4.DefaultIfEmpty()
orderby (new
{
TXT_Property = g.Property,
TXT_Product = Coalesce((Coalesce(a4.Page, "") == "" ? Coalesce(a4.Product, a3.Product) : Coalesce(a4.Product, "SA")), a3.Product, (Coalesce(a2.Page, "") == "" ? Coalesce(a2.Product, a1.Product) : Coalesce(a2.Product, "SA")), a1.Product),
TXT_Language = Coalesce(a4.Language, a3.Language, a2.Language, a1.Language),
})
select (new
{
TXT_Property = g.Property,
TXT_Product = Coalesce((Coalesce(a4.Page, "") == "" ? Coalesce(a4.Product, a3.Product) : Coalesce(a4.Product, "SA")), a3.Product, (Coalesce(a2.Page, "") == "" ? Coalesce(a2.Product, a1.Product) : Coalesce(a2.Product, "SA")), a1.Product),
TXT_Language = Coalesce(a4.Language, a3.Language, a2.Language, a1.Language),
TXT_Value = Coalesce(a4.Value, a3.Value, a2.Value, a1.Value)
}));
答案 0 :(得分：1)
你的SQL查询对我来说似乎很有疑问（因为ux是LEFT JOIN并且（可能）在查询的其余部分没有引用，它什么都没有添加），我不得不假设ORDER BY是g列，因为它没有指定（我感到惊讶的是，SQL没有被拒绝模糊），但这是我在翻译时的尝试：
var ans = from g in MD
join ux in MD on new { TXT_Page = sPage, g.TXT_Property, TXT_Product = sProdAll, GID_Section = (string)null } equals new { ux.TXT_Page, ux.TXT_Property, ux.TXT_Product, ux.GID_Section } into uxj
from ux in uxj.DefaultIfEmpty()
join up in MD on new { TXT_Page = sPage, g.TXT_Property, GID_Section = (string)null } equals new { up.TXT_Page, up.TXT_Property, up.GID_Section } into upj
from up in upj.DefaultIfEmpty()
where up == null || (up.TXT_Product ?? "") == sProd || up.TXT_Product == sProdAlt
where g.GID_Section == null && g.TXT_Page == sPage &&
((g.TXT_Product ?? "") == sProd || g.TXT_Product == sProdAlt || g.TXT_Product == sProdAll)
orderby g.TXT_Property, g.TXT_Product, g.TXT_Language
select new { g.TXT_Property, up.TXT_Page };
注意：我输入了up == null，因为否则where可能会拒绝SQL中的LEFT JOIN不会的位置。
我认为GID_Section的类型为string，但您可以将null转换为正确的类型。
这是我的SQL转换配方，虽然你的SQL有点棘手，因为它结合了LEFT JOIN和非等值连接。
将SQL转换为LINQ查询理解：
FROM子选项翻译为单独声明的变量。DISTINCT，TOP，MIN，MAX等）转换为应用于整个LINQ查询的函数new { ... }）。JOIN条件不是AND的所有等式测试必须使用加入外的where子句或跨产品（from ... {来处理{1}} ...）然后from where两个表之间多个JOIN ed等式测试的条件应该转换为匿名对象AND使用LEFT JOIN joinvariable 进行模拟，然后从{{1>} joinvariable 进行另一次<{1}} into替换为条件运算符（from）和.DefaultIfEmpty()测试。COALESCE转换为?:和null转换为IN ... .Contains()，使用文字数组或数组变量作为常量列表。NOT IN low ! high 翻译为 low {{1 } x Contains() x BETWEEN high 。AND翻译为三元条件运算符<=。&&必须替换为select range_variable或者连接，一个包含所有范围变量的匿名对象。<=字段必须替换为CASE ... ?:，以创建包含所有所需字段或表达式的匿名对象。SELECT *。