如何查詢數據庫以及如何通過第二個查詢聯接結果（VB.NET）

Question

我是VB.NET的新手，我希望這是一個簡單的問題。 我正在嘗試查詢數據庫，將結果存儲到數據集，然后查詢同一數據庫，並為刪除任務加入結果。 如果有人有時間可以幫助，這就是我到目前為止的情況。 提前致謝。 也; 我更喜歡了解自己做錯了什么，而不是只是告訴我如何解決。

   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

---

還沒有完全解決它，但是我想我越來越近了。 我在cmdB.ExecuteNonQuery上收到“記錄已刪除”錯誤。 它創建/填充了tmp表，但是沒有任何內容被刪除。

更新的代碼：

    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的函數原型時，我無法想象這會填滿數據庫中的表，而是可以在.NET中進行迭代的客戶端數據集。

與其嘗試對客戶端結果集執行聯接，不如使用SQL創建臨時表是否合適？ 許多RDBMS都支持這種功能。 特別是想到的方言是：

SELECT * INTO #tempTable FROM table;

這不會返回結果集，而是在連接上填充臨時表（可能在基於數據庫系統的事務中）。 然后可以將臨時表與該連接的其他表聯接，並在SQL / DML語句中使用。

除此之外，還不清楚在選擇和隨后執行的刪除之間的目標是什么。 這兩個查詢中的where子句相同，因此，如果在選擇刪除操作之間未執行任何處理或數據更改，則將兩者結合在一起的想法是不必要的。 可能您可以僅使用WHERE子句而不是聯接執行DELETE語句，並實現相同的目標。

希望這可以幫助！

Answer 2

我已經使用SSMS重新整理了您的查詢，以提高格式和可讀性。 將它們重新集成到您的代碼中，看看它們是否有幫助。

  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 )

我會說我仍然對為什么使用tmp表或為什么要以這種方式刪除數據感到困惑。 但是試一下這些查詢，看看它們是否有幫助。

Answer 3

我有幾處錯了，但是我終於開始工作了。 這就是我最終得到的。

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