Question

我有一个查询应该返回“A”实体，同时链接到实体“B”和“C”，这两个链接有“左外连接”操作符，这样我就可以从一个链接接收“A”实体或其他。

执行后，它只返回一条记录，这对于两个链接标准是常见的。如果我删除实体“B”的链接，那么我会得到符合链接条件的预期记录。当我删除实体“C”的链接时，同时发生了与实体“B”的链接。

所以，我假设我的查询仅适用于一个链接，但是当有两个链接并且我不明白为什么时，它不能按预期工作。

实际上我正在关注MSDN example。

这是我的数据：

_____________
|     A     |
-------------
|   a_id    |
|     1     | - entity with this id is the only record in the results
|     2     | - entity with this id should appear in the results, but it is not
|     3     | - entity with this id should appear in the results, but it is not

_________________________________
|               B               |
---------------------------------
|   b_one_id    |   b_two_id    |
|       1       |       1       | - matches link criteria with alias "connectionB"
|       2       |       1       | - matches link criteria with alias "connectionB"
|       1       |       444     | - doesn't match link criteria, should not appear

_________________________________
|               C               |
---------------------------------
|   c_one_id    |   c_two_id    |
|       1       |       2       | - matches link criteria with alias "connectionC"
|       3       |       2       | - matches link criteria with alias "connectionC"
|       1       |       555     | - doesn't match link criteria, should not appear

我的查询表达式：

QueryExpression query = new QueryExpression
{
    EntityName = A.EntityLogicalName,
    ColumnSet = new ColumnSet
    {
        AllColumns = false,
        Columns =
        {
            "a_id",
            "a_name"
        }
    }
};

query.Distinct = true;

query.AddLink(B.EntityLogicalName, "a_id", "b_one_id", JoinOperator.LeftOuter);
query.LinkEntities[0].EntityAlias = "connectionB";
query.LinkEntities[0].LinkCriteria.AddCondition("b_two_id", ConditionOperator.Equal, 1);

query.AddLink(C.EntityLogicalName, "a_id", "c_one_id", JoinOperator.LeftOuter);
query.LinkEntities[0].EntityAlias = "connectionC";
query.LinkEntities[0].LinkCriteria.AddCondition("c_two_id", ConditionOperator.Equal, 2);

// doesn't work as expected
query.Criteria.AddFilter(LogicalOperator.Or);
query.Criteria.Filters[0].AddCondition("connectionB", "b_one_id", ConditionOperator.NotNull);
query.Criteria.Filters[0].AddCondition("connectionC", "c_one_id", ConditionOperator.NotNull);

// doesn't work as expected either
query.Criteria.AddCondition("a_id", ConditionOperator.NotNull);

查询表达式转换为以下Fetch XML查询：

<fetch distinct="true" no-lock="false" mapping="logical">
    <entity name="A">
        <attribute name="a_id" />
        <attribute name="a_name" />
        <filter type="and">
            <filter type="or">
                <!-- doesn't work as expected -->
                <condition attribute="b_one_id" operator="not-null" entityname="connectionB" />
                <condition attribute="c_one_id" operator="not-null" entityname="connectionC" />

                <!-- doesn't work as expected either -->
                <condition attribute="a_id" operator="not-null" entityname="A" />
            </filter>
        </filter>
        <link-entity name="B" to="a_id" from="b_one_id" link-type="outer" alias="connectionB">
            <filter type="and">
                <condition attribute="b_two_id" operator="eq" value="1" />
            </filter>
        </link-entity>
        <link-entity name="C" to="a_id" from="c_one_id" link-type="outer" alias="connectionC">
            <filter type="and">
                <condition attribute="c_two_id" operator="eq" value="2" />
            </filter>
        </link-entity>
    </entity>
</fetch>

Answer 1

我希望您的代码中存在一些编程错误。查看您的代码部分

query.AddLink(B.EntityLogicalName, "a_id", "b_one_id", JoinOperator.LeftOuter);
query.LinkEntities[0].EntityAlias = "connectionB";
query.LinkEntities[0].LinkCriteria.AddCondition("b_two_id", ConditionOperator.Equal, 1);

query.AddLink(C.EntityLogicalName, "a_id", "c_one_id", JoinOperator.LeftOuter);
query.LinkEntities[0].EntityAlias = "connectionC";
query.LinkEntities[0].LinkCriteria.AddCondition("c_two_id", ConditionOperator.Equal, 2);

您正在添加query.AddLink（）并再次添加一些其他链接以进行查询但是为Alias和LinkCriteria使用相同的链接即query.LinkEntities [0]。可能是纠正这个错误可以解决你的问题。

查询以使用Left Outer Join返回与两个链接标准匹配的实体

1 个答案: