如何查询数据库以及如何通过第二个查询联接结果（VB.NET）

Question

我是VB.NET的新手，我希望这是一个简单的问题。 我正在尝试查询数据库，将结果存储到数据集，然后查询同一数据库，并为删除任务加入结果。 如果有人有时间可以帮助，这就是我到目前为止的情况。 提前致谢。 也; 我更喜欢了解自己做错了什么，而不是只是告诉我如何解决。

   Private Sub cmdDelete_Click(sender As System.Object, e As System.EventArgs) Handles cmdDelete.Click
    'Set/Open Connection
    Dim con As OleDbConnection = New OleDbConnection("Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Users\youngje\Documents\SQL Server Management Studio\Projects\Nwind.accdb")
    con.Open()

    'Set TIMEID
    Dim Yr, Mnth, fRng As String
    Yr = Year(Now)
    Mnth = Format(Month(Now), "00")
    fRng = Yr + Mnth + "00"

    'Query 1/Fill Temp Table (tmp)
    Dim cmdA As OleDbCommand = New OleDbCommand("SELECT PRODUCT, SHIPTO, TIMEID " & _
                                                "FROM tblFactSales " & _
                                                "WHERE (BILLTO = 'INPUT_BILLTO') AND (BRANCHPLANT = 'INPUT_BRANCHPLANT') AND (FRTHANDLE = 'INPUT_FRTHANDLE') AND (DATATYPE = 'FORECAST') AND (TIMEID > '" & fRng & "' )" & _
                                                "AND (SIGNEDDATA >= - .01) AND (SIGNEDDATA <= .01) AND (SALESDATA = 'short_tons')", con)

    'Query 2, joined with Query 1
    Dim cmdB As OleDbCommand = New OleDbCommand("DELETE FS " & _
                                                "FROM tblFactSales as FS INNER JOIN tmp T" & _
                                                "ON FS.PRODUCT=T.PRODUCT AND FS.SHIPTO=T.SHIPTO AND FS.TIMEID=T.TIMEID " & _
                                                "WHERE (FS.DATATYPE = 'FORECAST') AND (FS.TIMEID > '" & fRng & "' )", con)


    'Execute Queries
    cmdA.ExecuteNonQuery()
    cmdB.ExecuteNonQuery()

    'Clean Up
    cmdA.Dispose()
    cmdB.Dispose()
    con.Close()
    GC.Collect()

    'Confirmation
    MessageBox.Show("Records Removed Successfully.", "Clear Complete", _
        MessageBoxButtons.OK, MessageBoxIcon.Information, MessageBoxDefaultButton.Button1)
End Sub

---

还没有完全解决它，但是我想我越来越近了。 我在cmdB.ExecuteNonQuery上收到“记录已删除”错误。 它创建/填充了tmp表，但是没有任何内容被删除。

更新的代码：

    Private Sub cmdDelete_Click(sender As System.Object, e As System.EventArgs) Handles cmdDelete.Click
    'Set/Open Connection
    Dim con As OleDbConnection = New OleDbConnection("Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Users\youngje\Documents\SQL Server Management Studio\Projects\Nwind.accdb")
    con.Open()

    'Set TIMEID
    Dim Yr, Mnth, fRng As String
    Yr = Year(Now)
    Mnth = Format(Month(Now), "00")
    fRng = Yr + Mnth + "00"

    'SELECT, to find unique IDs (PRODUCT, SHIPTO, TIMEID, DATATYPE)
    Dim cmdA As OleDbCommand = New OleDbCommand("SELECT PRODUCT, SHIPTO, TIMEID, DATATYPE INTO tmp IN 'C:\Users\youngje\Documents\SQL Server Management Studio\Projects\Nwind.accdb'" & _
                                                "FROM tblFactSales " & _
                                                "WHERE (BILLTO = 'INPUT_BILLTO') AND (BRANCHPLANT = 'INPUT_BRANCHPLANT') AND (FRTHANDLE = 'INPUT_FRTHANDLE') AND (DATATYPE = 'FORECAST') AND (TIMEID >= '" & fRng & "' )" & _
                                                "AND (SIGNEDDATA >= - .01) AND (SIGNEDDATA <= .01) AND (SALESDATA = 'short_tons')", con)

    'DELETE, joined with cmdA results
    Dim cmdB As OleDbCommand = New OleDbCommand("DELETE tblFactSales.* " & _
                                                "FROM tblFactSales INNER JOIN tmp T " & _
                                                "ON tblFactSales.PRODUCT=T.PRODUCT AND tblFactSales.SHIPTO=T.SHIPTO AND tblFactSales.TIMEID=T.TIMEID", con)

    'Execute Queries
    cmdA.ExecuteNonQuery()
    cmdB.ExecuteNonQuery()

    'Clean Up
    cmdA.Dispose()
    cmdB.Dispose()
    con.Close()
    GC.Collect()

    'Confirmation
    MessageBox.Show("Records Removed Successfully.", "Clear Complete", _
        MessageBoxButtons.OK, MessageBoxIcon.Information, MessageBoxDefaultButton.Button1)

End Sub

Answer 1

我不是很肯定，但是在查看DataAdapter.Fill的函数原型时，我无法想象这会填满数据库中的表，而是可以在.NET中进行迭代的客户端数据集。

与其尝试对客户端结果集执行联接，不如使用SQL创建临时表是否合适？ 许多RDBMS都支持这种功能。 特别是想到的方言是：

SELECT * INTO #tempTable FROM table;

这不会返回结果集，而是在连接上填充临时表（可能在基于数据库系统的事务中）。 然后可以将临时表与该连接的其他表联接，并在SQL / DML语句中使用。

除此之外，还不清楚在选择和随后执行的删除之间的目标是什么。 这两个查询中的where子句相同，因此，如果在选择删除操作之间未执行任何处理或数据更改，则将两者结合在一起的想法是不必要的。 可能您可以仅使用WHERE子句而不是联接执行DELETE语句，并实现相同的目标。

希望这可以帮助！

Answer 2

我已经使用SSMS重新整理了您的查询，以提高格式和可读性。 将它们重新集成到您的代码中，看看它们是否有帮助。

  INSERT  INTO tmp
        (
         PRODUCT
        ,SHIPTO
        ,TIMEID
        ,DATATYPE
        )
        SELECT  PRODUCT
               ,SHIPTO
               ,TIMEID
               ,DATATYPE
        FROM    tblFactSales
        WHERE   (BILLTO = 'INPUT_BILLTO')
                AND (BRANCHPLANT = 'INPUT_BRANCHPLANT')
                AND (FRTHANDLE = 'INPUT_FRTHANDLE')
                AND (DATATYPE = 'FORECAST')
                AND (TIMEID >= ' & fRng & ')
                AND (SIGNEDDATA >= -.01)
                AND (SIGNEDDATA <= .01)
                AND (SALESDATA = 'short_tons')

DELETE  tblFactSales
WHERE   EXISTS ( SELECT 'True'
                 FROM   tmp T
                 WHERE  tblFactSales.PRODUCT = T.PRODUCT
                        AND tblFactSales.SHIPTO = T.SHIPTO
                        AND tblFactSales.TIMEID = T.TIMEID )

我会说我仍然对为什么使用tmp表或为什么要以这种方式删除数据感到困惑。 但是试一下这些查询，看看它们是否有帮助。

Answer 3

我有几处错了，但是我终于开始工作了。 这就是我最终得到的。

Private Sub cmdDelete_Click(sender As System.Object, e As System.EventArgs) Handles cmdDelete.Click

    Dim Con As SqlConnection = New SqlConnection("Server = OVP-L-R8MXE5M\SQLEXPRESS;" & "Database = dbTest;" & "Trusted_Connection=TRUE")
    Con.Open()

    Dim Yr, Mnth, fRng As String
    Yr = Year(Now)
    Mnth = Format(Month(Now), "00")
    fRng = Yr + Mnth + "00"

    Dim cmdA As SqlCommand = New SqlCommand("SELECT PRODUCT, SHIPTO, TIMEID, DATATYPE INTO tmp " & _
                                                "FROM tblFactSales " & _
                                                "WHERE (BILLTO = 'INPUT_BILLTO') AND (BRANCHPLANT = 'INPUT_BRANCHPLANT') AND (FRTHANDLE = 'INPUT_FRTHANDLE') AND (DATATYPE = 'FORECAST') AND (RPTCURRENCY = 'USD') AND (TIMEID >= '" & fRng & "') " & _
                                                "AND (SIGNEDDATA >= - .01) AND (SIGNEDDATA <= .01) AND (SALESDATA = 'short_tons')", Con)

    Dim cmdB As SqlCommand = New SqlCommand("DELETE tblFactSales " & _
                                                "FROM tblFactSales RIGHT JOIN tmp " & _
                                                "ON tblFactSales.PRODUCT=tmp.PRODUCT AND tblFactSales.SHIPTO=tmp.SHIPTO AND tblFactSales.TIMEID=tmp.TIMEID AND tblFactSales.DATATYPE=tmp.DATATYPE", Con)

    cmdA.ExecuteNonQuery()
    cmdB.ExecuteNonQuery()

    MessageBox.Show("Records Removed Successfully.", "Clear Complete", _
        MessageBoxButtons.OK, MessageBoxIcon.Information, MessageBoxDefaultButton.Button1)

End Sub