Question

我有SQL表（有更多列，但并不重要）

CREATE TABLE `test_results` (
`id` int AUTO_INCREMENT,
`date_time` datetime,
`altpn` varchar(60),
`error1` int,
`error2` int,
`error3` int,
PRIMARY KEY (`id`)
);

数据可以是：id，2016-06-16 14：26：02,9513 400,590,0,0。

在此表上运行此SQL查询：

SELECT date(test_results.date_time) AS date, test_results.altpn as PN, COUNT(*) AS count 
FROM test_results 
WHERE (test_results.error1 = 1000 OR test_results.error1 = 1001 OR test_results.error2 = 1000 OR test_results.error2 = 1001 OR test_results.error3 = 1000 OR test_results.error3 = 1001) 
GROUP BY date(test_results.date_time), test_results.altpn 
ORDER BY date(test_results.date_time), test_results.altpn

这可行，但我还需要知道COUNT(*)为零时的日期。我看到关于LEFT JOIN的几个主题，但我无法修改代码以使用此表。

Answer 1

使用WHERE时，会过滤出包含其他错误代码的行，并且无法对其进行计数。而是像往常一样选择所有行，并将LEFT JOIN选择到不存在零行的表：

#Region "Merge Combo's"

    Private Sub List_Merge_Click(sender As Object, e As EventArgs) Handles List_Merge.Click

        Dim ofd = New OpenFileDialog()
        ofd.Title = "Import..."
        ofd.InitialDirectory = Environment.GetFolderPath(Environment.SpecialFolder.Desktop)
        ofd.Filter = "Text files|*.txt"
        ofd.Multiselect = True

        'If the user selects 2 Files;
        If (ofd.ShowDialog() = DialogResult.OK And ofd.CheckFileExists = True) Then

            'Make sure there are no previously stored Conversions;
            ActionList2.Items.Clear()

            'Variables;
            Dim MergedCombos As Integer = 0
            Dim TotalCombos As Integer = 0

            Try

                For Each filename As String In ofd.FileNames

                    Using sr As New StreamReader(filename)

                        Dim result = filename.Union(filename, New MailEqualityComparer)

                        'Get all Matches found from the Regex Condition;
                        Dim combos As MatchCollection = New Regex("^([^@]+)@(.*):(.*)$", RegexOptions.Multiline).Matches(sr.ReadToEnd)

                        'Add each Match to the ActionList except for Duplicates;
                        For Each combo As Match In combos

                            'Increment the Total Combo's count;
                            TotalCombos += 1

                            'If the ActionList doesn't contain the same Combo;
                            If Not ActionList2.Items.Contains(combo.Value) Then

                                'If the email is already in the ActionList;
                                If IsInListbox(ActionList2, combo.Groups(1).Value + "@" + combo.Groups(2).Value) = True Then

                                    'This combo is presumed to be a Hash Decrypted Combo - Overwrite it with the Encrypted Hash;
                                    ActionList2.Items.Add(combo.Value)

                                    'Remove the Hash Item from ActionList;
                                    ActionList2.Items.RemoveAt(FindListboxIndex(ActionList2, combo.Groups(1).Value + "@" + combo.Groups(2).Value))

                                Else

                                    'Add the Combo;
                                    ActionList2.Items.Add(combo.Value)

                                End If

                            End If

                        Next

                    End Using

                Next

            Catch ex As Exception

                Console.WriteLine("Error: " + ex.ToString)

            Finally

                'If atleast 1 Item is in the ActionList, Enable the Export Button;
                If ActionList2.Items.Count > 0 Then
                    ExportButton.Enabled = True
                    ExportButton.BackColor = Color.FromArgb(149, 255, 141)
                End If

                'Update the Merged Combo's count;
                StatusBar_LeftText.Text = MergedCombos.ToString

                'If MergedCombos are less than TotalCombos, Add a "x Duplicates Removed" message;
                If MergedCombos < TotalCombos Then
                    StatusBar_LeftText.Text += " - " + (TotalCombos - MergedCombos).ToString + " Duplicates Removed"
                End If

                'Autoscroll;
                ActionList2.TopIndex = ActionList2.Items.Count - 1

            End Try

        End If

    End Sub

    Private Function FindListboxIndex(lb As ListBox, searchString As String) As Integer
        For i As Integer = 0 To lb.Items.Count - 1
            If lb.Items(i).ToString().Contains(searchString) Then
                Return i
                Exit Function
            End If
        Next
        Return -1
    End Function

    Private Function IsInListbox(lb As ListBox, searchString As String) As Boolean
        For i As Integer = 0 To lb.Items.Count - 1
            If lb.Items(i).ToString().Contains(searchString) Then
                Return True
                Exit Function
            End If
        Next
        Return False
    End Function

#End Region

如您所见，结果集包含错误为1000/1001的行和其他错误的NULL值。现在，只需将它们分组并计算：

SELECT * 
FROM test_results t1
LEFT JOIN test_results t2 ON t2.id=t1.id
  AND 
  (t2.error1 = 1000 OR t2.error1 = 1001 OR t2.error2 = 1000 
  OR t2.error2 = 1001 OR t2.error3 = 1000 OR t2.error3 = 1001)

http://sqlfiddle.com/#!9/9c6236/4

一个表中的SQL COUNT（*）包括零值

1 个答案: