Add a note on querying shared columns

entity-framework/core/modeling/inheritance.md

@@ -55,6 +55,9 @@ By default, when two sibling entity types in the hierarchy have a property with
 
 [!code-csharp[Main](../../../samples/core/Modeling/FluentAPI/SharedTPHColumns.cs?name=SharedTPHColumns&highlight=9,13)]
 
+> [!NOTE]
+> Relational database providers, such as SQL Server, will not automatically use the discriminator predicate when querying shared columns when using a cast. The query `Url = (blob as RssBlog).Url` would also return the `Url` value for the sibling `Blog` rows. To restrict the query to `RssBlog` entities you need to manually add a filter on the discriminator, such as `Url = blob is RssBlog ? (blob as RssBlog).Url : null`.
+
 ## Table-per-type configuration
 
 > [!NOTE]