Question

我有一个从用户输入构建SQL语句的表单。控件包括CheckBox，TextBox，ComboBox和DateTimePicker。

它们分组在表单的每个部分的全局数组中。一些语句将检查SQL命令的多个控件。

现在我使用一堆if ... else if语句来构建我的SQL语句，检查检查状态，文本更改等等。但是，如果更改数组中的控制索引，则此方法已证明不稳定。

我正在寻找一种更简单的方法来一次构建SQL语句。每次控件的状态发生变化时，我都想过为每个控件组更改一个字符串，从而在用户想要运行时不需要构建SQL，但是我不确定这是不是一个很好的方法处理它。

我目前使用的方法有替代方法吗？那个我一直在考虑转而值得努力的人吗？

编辑：根据要求，这里是我目前使用的一些代码。

'icControls is the class that has all of the global arrays
'DefaultStrings is the module that has the default strings in the textboxes

Dim sqlWhere As String = "Where "
If Me._icControls.chkBasic(0).Checked = True And Me._icControls.chkBasic(1).Checked = True _
                And Me._icControls.chkBasic(2).Checked = True Then
        sqlWhere += """Field1"" in('A', 'B', 'C')"
ElseIf Me._icControls.chkBasic(0).Checked = True And Me._icControls.chkBasic(1).Checked = True Then
        sqlWhere += """Field1"" in('A', 'B')"
ElseIf Me._icControls.chkBasic(0).Checked = True And Me._icControls.chkBasic(2).Checked = True Then
        sqlWhere += """Field1"" in('A', 'C')"
ElseIf Me._icControls.chkBasic(1).Checked = True And Me._icControls.chkBasic(2).Checked = True Then
        sqlWhere += """Field1"" in('B', 'C')"
ElseIf Me._icControls.chkBasic(0).Checked = True Then
        sqlWhere += """Field1"" in('A')"
        sqlWhere += " AND (SUBSTR(""Tag #"", 1, 1) not in('#') and ""Inventory Type"" in('F'))"
ElseIf Me._icControls.chkBasic(1).Checked = True Then
        sqlWhere += """Field1"" in('B')"
        sqlWhere += " AND (SUBSTR(""Tag #"", 1, 1) in('R', 'A', 'Z') and ""Inventory Type"" in('R'))"
ElseIf Me._icControls.chkBasic(2).Checked = True Then
        sqlWhere += """Field1"" in('')"
        sqlWhere += " AND (SUBSTR(""Tag #"", 1, 1) in('W'))"
End If

If Me._icControls.chkBasic(4).Checked = True And Me._icControls.chkBasic(5).Checked = True Then
        sqlWhere += " AND ""Field2"" in('A', 'B')"
ElseIf Me._icControls.chkBasic(4).Checked = True Then
        sqlWhere += " AND ""Field2"" in('A')"
ElseIf Me._icControls.chkBasic(5).Checked = True Then
        sqlWhere += " AND ""Field2"" in('B')"
End If

If Me._icControls.chkBasic(6).Checked = True And Me._icControls.chkBasic(7).Checked = True Then
        sqlWhere += " AND ""Field3"" in('A', 'B')"
ElseIf Me._icControls.chkBasic(6).Checked = True Then
        sqlWhere += " AND ""Field3"" in('A')"
ElseIf Me._icControls.chkBasic(7).Checked = True Then
        sqlWhere += " AND ""Field3"" in('B')"
End If

If Me._icControls.txtMaterial(0).Text.ToString() <> DefaultStrings.Material(0) Then
        sqlWhere += " AND ""Material"" in('" + Me._icControls.txtMaterial(0).Text.ToString() + "')"
End If

Answer 1

我在评论中提出的解决方案将包括以下步骤：

创建列表＆lt;元组＆lt; string，List＆gt;＆gt; selectValues，每个字段包含一个项目，每个项目（一个元组）由字段名称和字段值组成。
创建元组＆lt;串，列表＆gt; field1Values = new Tuple＆lt;＆＃34; Field1，field1Values＆gt;和内部列表。将field1Values添加到selectValues
循环_icControls.chkBasic项目并将项目值添加到field1值List，
field2Values，field3Values，...
在SelectValues上循环，忽略带有空列表的字段以构建SQL命令：从元组的element1获取字段名称，从element2中包含的列表中获取值。

Answer 2

我认为仅在您需要时（按下按钮后）生成SQL语句的方法比每次值更改时生成它更好。那你每次都不需要检查价值，
检查它并将结果保存到变量

Dim chkControl0 As CheckBox
Dim chkControl1 As CheckBox
Dim chkControl2 As CheckBox
Dim chkControl3 As CheckBox
Dim chkControl4 As CheckBox
Dim chkControl5 As CheckBox
Dim chkControl6 As CheckBox
Dim chkControl7 As CheckBox

Private Function GenerateField1WhereClause() As String
    Const CHK0 As String = "'A'"
    Const CHK1 As String = "'B'"
    Const CHK2 As String = "'C'"
    Dim checked As New List(Of String)()
    If chkControl0.Checked = True Then checked.Add(CHK0)
    If chkControl1.Checked = True Then checked.Add(CHK1)
    If chkControl2.Checked = True Then checked.Add(CHK2)
    If checked.Count = 0 Then Return String.Empty
    If checked.Count = 1 Then
        Select Case checked(0)
            Case CHK0
                Return String.Format("""Field1"" = {0} AND (SUBSTR(""Tag #"", 1, 1) NOT IN('#') AND ""Inventory Type"" IN ('F'))", CHK0)
            Case CHK1
                Return String.Format("""Field1"" = {0} AND (SUBSTR(""Tag #"", 1, 1) in('R', 'A', 'Z') and ""Inventory Type"" in('R'))", CHK1)
            Case CHK2
                Return String.Format("""Field1"" = {0} AND (SUBSTR(""Tag #"", 1, 1) in('R', 'A', 'Z') and ""Inventory Type"" in('R'))", CHK2)
        End Select
        String.Format("Field1 = {0} AND (SUBSTR(""Tag #"", 1, 1) in('W'))")
    Else
         Return String.Format("""Field1""  IN ({0})", String.Join(",", checked))
    End If
End Function

Private Function GenerateField2WhereClause() As String
    Const CHK0 As String = "'A'"
    Const CHK1 As String = "'B'"
    Dim checked As New List(Of String)()
    If chkControl4.Checked = True Then checked.Add(CHK0)
    If chkControl5.Checked = True Then checked.Add(CHK1)
    If checked.Count = 0 Then Return String.Empty
    Return String.Format("""Field2"" IN ({0})", String.Join(",", checked))
End Function

Private Function GenerateField3WhereClause() As String
    Const CHK0 As String = "'A'"
    Const CHK1 As String = "'B'"
    Dim checked As New List(Of String)()
    If chkControl6.Checked = True Then checked.Add(CHK0)
    If chkControl7.Checked = True Then checked.Add(CHK1)
    If checked.Count = 0 Then Return String.Empty
    Return String.Format("""Field3"" IN ({0})", String.Join(",", checked))
End Function

然后使用函数并检查结果是否为空，您可以创建WHERE子句

Private Function GenerateWhereClause() as String
    Dim where As New StringBuilder()
    Dim field1 As String = Me.GenerateField1WhereClause()
    If String.IsNullOrEmpty(field1) = false Then
        where.Append(field1)
    End If
    Dim field2 As String = Me.GenerateField2WhereClause()
    If String.IsNullOrEmpty(field2) = false Then
        If where.length > 0 Then where.Append(" AND ")
        where.Append(field2)
    End If
    Dim field3 As String = Me.GenerateField3WhereClause()
    If String.IsNullOrEmpty(field3) = false Then
        If where.length > 0 Then where.Append(" AND ")
        where.Append(field3)
    End If
    If where.Length > 0 Then where.Insert(0, "WHERE ")
    Return where.ToString()
End Function

如果您需要表单外部复选框的值，只需创建一个仅返回值

的属性

Public ReadOnly Property Check0 As Boolean
    Return Me.chkControl0.Checked
End property

从VB.net表单构建SQL语句的简单方法？

2 个答案: