DataSet - 在填充外连接查询时确保 PrimaryKey 数据

发布于 2024-09-04 22:02:44 字数 899 浏览 7 评论 0原文

填充数据集时，我使用 DataAdapter 的 MissingSchemaAction 的“AddWithKey”值。根据 MSDN：

将架构信息添加到数据集在填充数据之前确保主键约束是包含在 DataTable 对象中数据集。

但是，当我执行以下操作时：

DataColumn[] foo = TheDataSet.Tables["Table1"].PrimaryKey;

我得到 foo.Length 为 0。除此之外我还需要做些什么吗？：

string TheQuery = "SELECT * FROM Table1 LEFT OUTER JOIN Table2 ON Table1.EVENT_NUM = Table2.EVENT_USER_NUM;
using (SqlDataAdapter TheDataAdapter = new SqlDataAdapter(TheQuery, TheConnection)
{
    TheDataAdapter.MissingSchemaAction = MissingSchemaAction.AddWithKey;
    TheDataAdapter.Fill(TheDataSet, "Table1");
}

注意，如果我的查询是：

string TheQuery = "SELECT * FROM Table1";

一切都会好的。但是，如果有连接，我不会得到主键。这是否可能（获取主键）？

编辑：起初，我没有意识到这是一个 JOIN。不过，我已经测试了会返回 PrimaryKey 的 INNER JOINS。罪魁祸首似乎是因为这是一个 OUTER JOIN。因此，我改变了标题。

原文

When filling a DataSet, I am using the "AddWithKey" value for the DataAdapter's MissingSchemaAction. According to MSDN:

Adding schema information to a DataSet
before filling it with data ensures
that primary key constraints are
included with the DataTable objects in
the DataSet.

But, when I do the following:

DataColumn[] foo = TheDataSet.Tables["Table1"].PrimaryKey;

I get foo.Length of 0. Is there something more that I need to do besides this?:

string TheQuery = "SELECT * FROM Table1 LEFT OUTER JOIN Table2 ON Table1.EVENT_NUM = Table2.EVENT_USER_NUM;
using (SqlDataAdapter TheDataAdapter = new SqlDataAdapter(TheQuery, TheConnection)
{
    TheDataAdapter.MissingSchemaAction = MissingSchemaAction.AddWithKey;
    TheDataAdapter.Fill(TheDataSet, "Table1");
}

Note, if my query was:

string TheQuery = "SELECT * FROM Table1";

All would be fine. But, I don't get a PrimaryKey if there is a join. Is this even possible (to get the Primary key)?

EDIT: At first, I didn't realize this was a JOIN. Although, I've tested INNER JOINS that would return a PrimaryKey. The culprit seems to be the fact that this is an OUTER JOIN. Thus, I changed the title.

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