[英]How do I join with OR condition?
這是我的LINQ代碼:
from b in dbContext.SAPBillOfMaterials
from t in dbContext.AUXComponentTypes
where t.ParentId == b.Parent.Id &&
t.MaterialType == b.Component.MaterialType &&
(t.ComponentCategoryCode == null || t.ComponentCategoryCode == b.Component.ComponentCategoryCode)
select new
{
ComponentCode = b.Component.Model_ComponentCode,
Grid = b.Component.Grid ,
ComponentType = t.ComponentType,
ConfigurationId = configId,
ParentSKUId = b.Parent.Id ,
SKUId = b.Component.Id
};
這是LINQ to Entities翻譯:
SELECT
[Extent2].[ParentId] AS [ParentId],
[Extent4].[Model_ComponentCode] AS [Model_ComponentCode],
[Extent4].[Grid] AS [Grid],
[Extent2].[ComponentType] AS [ComponentType],
[Extent1].[Parent_Id] AS [Parent_Id],
[Extent1].[Component_Id] AS [Component_Id]
FROM [dbo].[SAPBillOfMaterial] AS [Extent1]
INNER JOIN [dbo].[AUXComponentTypes] AS [Extent2] ON [Extent1].[Parent_Id] = [Extent2].[ParentId]
INNER JOIN [dbo].[SAPMasterMaterialSKU] AS [Extent3] ON ([Extent2].[MaterialType] = [Extent3].[MaterialType])
AND ([Extent1].[Component_Id] = [Extent3].[Id])
**AND ([Extent2].[ComponentCategoryCode] = [Extent3].[ComponentCategoryCode])**
LEFT OUTER JOIN [dbo].[SAPMasterMaterialSKU] AS [Extent4] ON [Extent1].[Component_Id] = [Extent4].[Id]
所以,它完全忽略了連接中的OR條件:
(t.ComponentCategoryCode == null || t.ComponentCategoryCode == b.Component.ComponentCategoryCode)
有人能告訴我為什么或我做錯了什么?
更新這里是我的模型的簡化版本:
public class AUXComponentType
{
[Key]
public int Id { get; set; }
[Required, ForeignKey("SAPMasterMaterialSKU")]
public int ParentId { get; set; }
public virtual SAPMasterMaterialSKU SAPMasterMaterialSKU { get; set; }
[Required,StringLength(4)]
public string MaterialType { get; set; }
[Required, StringLength(1)]
public string ComponentType { get; set; }
[Required, StringLength(20)]
public string ComponentCategoryCode { get; set; }
}
public class SAPBillOfMaterial
{
[Key, Column(Order = 1)]
public int Id { get; set; }
[InverseProperty("SAPBOMChilds"), Column(Order = 2)]
public virtual SAPMasterMaterialSKU Parent { get; set; }
[InverseProperty("SAPBOMs"), Column(Order = 3)]
public virtual SAPMasterMaterialSKU Component { get; set; }
public decimal Quantity { get; set; }
}
public class SAPMasterMaterialSKU
{
[Key]
public int Id { get; set; }
[Required,MaxLength(18)]
public string Model_ComponentCode { get; set; }
[MaxLength(8)]
public string Grid { get; set; }
[Required,MaxLength(4)]
public string MaterialType { get; set; }
[Required, MaxLength(20)]
public string ComponentCategoryCode { get; set; }
public virtual ICollection<SAPBillOfMaterial> SAPBOMChilds { get; set; }
public virtual ICollection<SAPBillOfMaterial> SAPBOMs { get; set; }
public virtual ICollection<AUXComponentType> AUXComponentTypes { get; set; }
}
從SQL LINQ中獲取SQL是一個多步驟的過程,因此要確定轉換某些操作的位置並不總是很容易。 LINQ創建了一個與語言無關的表達式樹,它將傳遞給EF運行時。 EF然后創建一個“cannonical”查詢表達式樹。 這樣做的原因是EF可以在幕后使用許多不同的DB ADO提供者之一,所以在這一點上,它只是獲得了可以在數據庫上使用的通用表達式樹。 然后它將此“cannonical”查詢表達式傳遞給EF ADO Provider,后者又生成實際的SQL語句。
在其中一個傳遞期間,你的OR條件被“優化”了,我懷疑它與LINQ處理連接的方式有關。 在你的情況下,在LINQ語句中沒有實際的JOIN子句,我懷疑它默認是做一個內連接,技術上不能讓連接的一邊有NULL(連接的兩邊必須在內連接中匹配)。
你真正想要的是OUTER JOIN,其中一方允許有NULL。 如果您在Internet上查詢LINQ和OUTER JOIN,您將獲得一些如何創建LINQ語句的示例,以允許其中一個邊包含NULL。
是否有可能擁有AUXComponentTypes.ComponentCategoryCode == null? 該字段是否標記為不可為空?
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