sql - 在 Access DB 中将字段拆分为多条记录

Question

我有一个 MS Access 数据库，其中有一个名为 Field1 的字段包含由逗号分隔的多个值。 IE。，
Value1,Value 2, Value3, Value 4,Value5
我试图不将值拆分为单独的字段，而是通过复制记录并将每个值存储在另一个字段中。这将使得包含具有三个值的单元格的记录将被复制三次，每条记录的值都在新字段中包含的值中变化。例如，

在查询/运行模块之前:
+-----------+------------------------+
| App Code | Field1 |
+-----------+------------------------+
| AB23 | Value1, Value 2,Value3 |
+------------------------------------+
查询/运行模块后:
+-----------------------------------------------+
| App Code | Field1 | Field2 |
+-----------+------------------------+----------+
| AB23 | Value1, Value 2,Value3 | Value1 |
+-----------+------------------------|----------+
| AB23 | Value1, Value 2,Value3 | Value 2 |
+-----------+------------------------+----------+
| AB23 | Value1, Value 2,Value3 | Value3 |
+-----------+------------------------+----------+
到目前为止，我发现了几个关于拆分字段的问题into two甚至several不同的字段，但我还没有找到任何垂直分割记录的解决方案。在这些解决方案中，一些使用查询，另一些使用模块，但我也不确定哪个最有效，所以我决定使用 VBA 模块。

因此，这是迄今为止我发现最有用的 VBA 模块:

Function CountCSWords (ByVal S) As Integer
      ' Counts the words in a string that are separated by commas.

      Dim WC As Integer, Pos As Integer
         If VarType(S) <> 8 Or Len(S) = 0 Then
           CountCSWords = 0
           Exit Function
         End If
         WC = 1
         Pos = InStr(S, ",")
         Do While Pos > 0
           WC = WC + 1
           Pos = InStr(Pos + 1, S, ",")
         Loop
         CountCSWords = WC
      End Function

      Function GetCSWord (ByVal S, Indx As Integer)
      ' Returns the nth word in a specific field.

      Dim WC As Integer, Count As Integer, SPos As Integer, EPos As Integer
         WC = CountCSWords(S)
         If Indx < 1 Or Indx > WC Then
           GetCSWord = Null
           Exit Function
         End If
         Count = 1
         SPos = 1
         For Count = 2 To Indx
           SPos = InStr(SPos, S, ",") + 1
         Next Count
         EPos = InStr(SPos, S, ",") - 1
         If EPos <= 0 Then EPos = Len(S)
         GetCSWord = Trim(Mid(S, SPos, EPos - SPos + 1))
      End Function

然而，我如何在 Access Query 中使用它来实现上述预期结果？否则，除了查询(即仅使用 VBA 模块)之外，是否有更好的方法得出相同的结论？

编辑

Note that the primary key in the Table is Application Code and not autonumber. This primary key is textual and distinct. In order for a record to be split, this will require the primary key to be duplicated, which is fine.

Answer 1

这是在 Table1 中使用 Field1、Field2 的示例代码

Option Explicit

Public Sub ReformatTable()

    Dim db          As DAO.Database
    Dim rs          As DAO.Recordset
    Dim rsADD       As DAO.Recordset

    Dim strSQL      As String
    Dim strField1   As String
    Dim strField2   As String
    Dim varData     As Variant
    Dim i           As Integer

    Set db = CurrentDb

    ' Select all eligible fields (have a comma) and unprocessed (Field2 is Null)
    strSQL = "SELECT Field1, Field2 FROM Table1 WHERE ([Field1] Like ""*,*"") AND ([Field2] Is Null)"

    Set rsADD = db.OpenRecordset("Table1", dbOpenDynaset, dbAppendOnly)

    Set rs = db.OpenRecordset(strSQL, dbOpenDynaset)
    With rs
        While Not .EOF
            strField1 = !Field1
            varData = Split(strField1, ",") ' Get all comma delimited fields

            ' Update First Record
            .Edit
            !Field2 = Trim(varData(0)) ' remove spaces before writing new fields
            .Update

            ' Add records with same first field 
            ' and new fields for remaining data at end of string
            For i = 1 To UBound(varData)
                With rsADD
                    .AddNew
                    !Field1 = strField1
                    !Field2 = Trim(varData(i)) ' remove spaces before writing new fields
                    .Update
                End With
            Next
            .MoveNext
        Wend

        .Close
        rsADD.Close

    End With

    Set rsADD = Nothing
    Set rs = Nothing
    db.Close
    Set db = Nothing

End Sub

编辑

Updated example to generate a new primary key

如果您必须根据以前的 Appcode 生成新的 AppCode(并且假设 AppCode 是一个文本字段)，您可以使用此示例根据最后一个 appcode 生成唯一的主键。

Option Explicit

Public Sub ReformatTable()

    Dim db          As DAO.Database
    Dim rs          As DAO.Recordset
    Dim rsADD       As DAO.Recordset

    Dim strSQL      As String
    Dim strField1   As String
    Dim strField2   As String
    Dim varData     As Variant
    Dim strAppCode  As String
    Dim i           As Integer

    Set db = CurrentDb

    ' Select all eligible fields (have a comma) and unprocessed (Field2 is Null)
    strSQL = "SELECT AppCode, Field1, Field2 FROM Table1 WHERE ([Field1] Like ""*,*"") AND ([Field2] Is Null)"

    ' This recordset is only used to Append New Records
    Set rsADD = db.OpenRecordset("Table1", dbOpenDynaset, dbAppendOnly)

    Set rs = db.OpenRecordset(strSQL, dbOpenDynaset)
    With rs
        While Not .EOF

            ' Do we need this for newly appended records?
            strAppCode = !AppCode

            strField1 = !Field1
            varData = Split(strField1, ",") ' Get all comma delimited fields

            ' Update First Field
            .Edit
            !Field2 = Trim(varData(0)) ' remove spaces before writing new fields
            .Update

            ' Add new fields for remaining data at end of string
            For i = 1 To UBound(varData)
                With rsADD

                    .AddNew

                    ' ***If you need a NEW Primary Key based on current AppCode
                    !AppCode = strAppCode & "-" & i

                    ' ***If you remove the Unique/PrimaryKey and just want the same code copied
                    !AppCode = strAppCode

                    ' Copy previous Field 1
                    !Field1 = strField1

                    ' Insert Field 2 based on extracted data from Field 1
                    !Field2 = Trim(varData(i)) ' remove spaces before writing new fields
                    .Update
                End With
            Next
            .MoveNext
        Wend

        .Close
        rsADD.Close

    End With

    Set rsADD = Nothing
    Set rs = Nothing
    db.Close
    Set db = Nothing

End Sub