VBA 中的索引 (Access 2003) - 字段关联
Indexing in VBA (Access 2003) - field association
基于 this tutorial page，Microsoft Access 如何知道为索引字段 collection 创建的字段关联到 TableDef 字段 collection 中的等效字段？
即使在 this Microsoft Support page 中，也会为索引 创建 字段，然后附加到索引的字段 collection:
...
'Copy Indexes
For I1 = 0 To SourceTableDef.Indexes.Count - 1
Set SI = SourceTableDef.Indexes(I1)
If Not SI.Foreign Then ' Foreign indexes are added by relationships
Set I = T.CreateIndex()
' Copy Jet Properties
On Error Resume Next
For P1 = 0 To I.Properties.Count - 1
I.Properties(P1).Value = SI.Properties(P1).Value
Next P1
On Error GoTo 0
' Copy Fields
For f1 = 0 To SI.Fields.Count - 1
Set F = T.CreateField(SI.Fields(f1).Name, T.Fields(SI.Fields(f1).Name).Type)
I.Fields.Append F
Next f1
T.Indexes.Append I
End If
Next I1
...
我不能简单地从 TableDef 的字段中添加现有字段 collection 吗？这没有什么意义，似乎也没有什么凝聚力。
更新
我实际上测试了代码 here 这基本上是我想做的......但是它失败了，并在这一行出现未定义的 object 错误：
Set F = T.CreateField(SI.Fields(f1).Name, T.Fields(SI.Fields(f1).Name).Type)
...当我们改变这个时，我们有各种各样的乐趣。
(23/05/2016) 此外，这个脚本似乎是错误的——第二个参数实际上不应该存在，这是不必要的。省略它会导致更多错误！哈！我的尾巴呢？我觉得我应该去追它。
我的问题的解决方案
我决定跟随 HansUp 的脚步并使用 DDL——这比尝试搜索与 objects 的操作相关的问题要容易得多（尽管在最终代码设计中有一定程度的这样）。 ..
Option Compare Database
Public Const cFname As String = "drm\drmData2016.accdb"
Public Const cPropNotFound As Integer = 3270
Public Const cNotSupported As Integer = 3251
Public Const cInvalidOp As Integer = 3219
Public Sub GenerateTables()
OpenLog
'Initalise...
Dim db As Database
Dim tdb As Database
Dim ts As TableDef, tt As TableDef
Dim p As Property
Dim f As Field, ft As Field
Dim i As Index
Dim s As String, t As String
Dim x As Boolean
Set db = CurrentDb
If Dir$(cFname) <> "" Then Kill cFname
Set tdb = Application.DBEngine.CreateDatabase(cFname, dbLangGeneral, dbVersion140)
WriteLog "Created database " & cFname & "."
'Create the tables...
WriteLog "Creating TableDefs...", 1
For Each ts In db.TableDefs
If Not StartsWith(ts.Name, "msys", "~", "$", "Name AutoCorrect") And Not EndsWith(ts.Name, "_xrep") Then
s = "SELECT "
For Each f In ts.Fields
If Not StartsWith(f.Name, "s_", "S_") Then s = s & "[" & f.Name & "], "
Next f
s = Left$(s, Len(s) - 2) & " INTO [" & ts.Name & "] IN """ & cFname & """ FROM [" & ts.Name & "];"
On Error Resume Next
db.Execute s
If Err.Number = 0 Then
WriteLog "Created [" & ts.Name & "] using " & s, 2
Else
WriteLog "Failed to create [" & ts.Name & "].", 2
WriteLog "Error " & Err.Number & ": " & Err.Description, 3
WriteLog "SQL: " & s, 3
Err.Clear
End If
tdb.TableDefs.Refresh
On Error GoTo 0
End If
Next ts
'Copy the properties...
WriteLog "Tables...", 1
For Each ts In db.TableDefs
If Not StartsWith(ts.Name, "msys", "~", "$", "Name Autocorrect") And Not EndsWith(ts.Name, "_xrep") Then
Set tt = tdb.TableDefs(ts.Name)
WriteLog ts.Name, 2
WriteLog "Table Properties...", 3
'Table properties...
For Each p In ts.Properties
On Error Resume Next
tt.Properties(p.Name) = p.value
If Err.Number = 0 Then
WriteLog p.Name & " = " & p.value, 3
Else
WriteLog "Error setting " & p.Name, 3
WriteLog Err.Number & ": " & Err.Description, 4
Err.Clear
End If
On Error GoTo 0
Next p
'Field properties...
WriteLog "Fields...", 3
For Each f In ts.Fields
If Not StartsWith(f.Name, "s_") Then
Set ft = tt.Fields(f.Name)
WriteLog f.Name, 3
WriteLog "Properties...", 3
For Each p In f.Properties
On Error Resume Next
ft.Properties(p.Name).value = p.value
Select Case Err.Number
Case 0
'Normal...
WriteLog p.Name & " = " & p.value, 4
Case cPropNotFound
'Create the property...
Dim np As Property
Set np = ft.CreateProperty(p.Name, p.Type, p.value)
ft.Properties.Append np
ft.Properties.Refresh
WriteLog "Created property " & p.Name & ", value of " & p.value, 4
Case cNotSupported, cInvalidOp
'We're not worried about these values - simply skip over them...
Case Else
WriteLog "Failed to create or change property " & p.Name & ".", 4
WriteLog "Error " & Err.Number & ": " & Err.Description, 5
Err.Clear
End Select
On Error GoTo 0
Next p
End If
Next f
'Create the indexes...
WriteLog "Table indexes...", 2
For Each i In ts.Indexes
x = False
s = "CREATE "
If i.Unique Then s = s & "UNIQUE "
s = s & "INDEX [" & i.Name & "] ON [" & ts.Name & "] ("
For Each f In i.Fields
s = s & "[" & f.Name & "], "
'Just make sure we're not dealing with replication fields...
x = StartsWith(f.Name, "s_")
Next f
'We only want
If Not x Then
WriteLog i.Name, 3
s = Left$(s, Len(s) - 2) & ") "
If i.Primary Or i.IgnoreNulls Or i.Required Then
s = s & "WITH "
If i.Primary Then s = s & "PRIMARY "
If i.IgnoreNulls Then s = s & "IGNORE NULL "
If i.Required Then s = s & "DISALLOW NULL "
End If
s = s & ";"
On Error Resume Next
tdb.Execute s
Select Case Err.Number
'Note: used select case just in case I need to add extra error numbers...
Case 0
'Normal...
WriteLog "Created index [" & i.Name & "] using " & s, 4
Case Else
WriteLog "Failed to create index [" & ts.Name & "].", 4
WriteLog "Error " & Err.Number & ": " & Err.Description, 5
WriteLog "SQL: " & s, 3
Err.Clear
End Select
On Error GoTo 0
End If
Next i
End If
Next ts
'Belt and braces tidy-up...
Set p = Nothing
Set f = Nothing
Set ft = Nothing
Set i = Nothing
Set ts = Nothing
Set tt = Nothing
tdb.Close
Set tdb = Nothing
Set db = Nothing
WriteLog "Closed database."
WriteLog "Finished.", , False
CloseLog
End Sub
总结：
索引（从 DAO 的角度来看）基本上是一种具有某些属性和字段名称及其数据类型的集合的数据结构。
它不是指向 tabledef 字段的指针的集合。
要通过 DAO 将字段添加到索引，需要一个字段对象，该对象由 CreateField() 创建。
索引对象也有一个 .CreateField() 方法，我认为这实际上是更常见的方法。
来自 http://allenbrowne.com/func-dao.html#CreateIndexesDAO :
'3. Multi-field index.
Set ind = tdf.CreateIndex("FullName")
With ind
.Fields.Append .CreateField("Surname")
.Fields.Append .CreateField("FirstName")
End With
tdf.Indexes.Append ind
请注意，this method 不采用 Type 和 Size 参数，仅采用 Name。我很乐意承认这一切有点令人困惑（或者语无伦次，如果你愿意的话）。
how does Microsoft Access know that a field created for an index
fields collection associates to an equivalent field in the TableDef
fields collection?
它根据名称进行检查。新索引字段的名称必须存在于 TableDef 中，并且该字段的数据类型必须是可索引的。如果不满足其中任何一个条件，您将收到一条错误消息。
基于 this tutorial page，Microsoft Access 如何知道为索引字段 collection 创建的字段关联到 TableDef 字段 collection 中的等效字段？
即使在 this Microsoft Support page 中，也会为索引 创建 字段，然后附加到索引的字段 collection:
...
'Copy Indexes
For I1 = 0 To SourceTableDef.Indexes.Count - 1
Set SI = SourceTableDef.Indexes(I1)
If Not SI.Foreign Then ' Foreign indexes are added by relationships
Set I = T.CreateIndex()
' Copy Jet Properties
On Error Resume Next
For P1 = 0 To I.Properties.Count - 1
I.Properties(P1).Value = SI.Properties(P1).Value
Next P1
On Error GoTo 0
' Copy Fields
For f1 = 0 To SI.Fields.Count - 1
Set F = T.CreateField(SI.Fields(f1).Name, T.Fields(SI.Fields(f1).Name).Type)
I.Fields.Append F
Next f1
T.Indexes.Append I
End If
Next I1
...
我不能简单地从 TableDef 的字段中添加现有字段 collection 吗？这没有什么意义，似乎也没有什么凝聚力。
更新
我实际上测试了代码 here 这基本上是我想做的......但是它失败了，并在这一行出现未定义的 object 错误：
Set F = T.CreateField(SI.Fields(f1).Name, T.Fields(SI.Fields(f1).Name).Type)
...当我们改变这个时，我们有各种各样的乐趣。
(23/05/2016) 此外，这个脚本似乎是错误的——第二个参数实际上不应该存在，这是不必要的。省略它会导致更多错误！哈！我的尾巴呢？我觉得我应该去追它。
我的问题的解决方案
我决定跟随 HansUp 的脚步并使用 DDL——这比尝试搜索与 objects 的操作相关的问题要容易得多（尽管在最终代码设计中有一定程度的这样）。 ..
Option Compare Database
Public Const cFname As String = "drm\drmData2016.accdb"
Public Const cPropNotFound As Integer = 3270
Public Const cNotSupported As Integer = 3251
Public Const cInvalidOp As Integer = 3219
Public Sub GenerateTables()
OpenLog
'Initalise...
Dim db As Database
Dim tdb As Database
Dim ts As TableDef, tt As TableDef
Dim p As Property
Dim f As Field, ft As Field
Dim i As Index
Dim s As String, t As String
Dim x As Boolean
Set db = CurrentDb
If Dir$(cFname) <> "" Then Kill cFname
Set tdb = Application.DBEngine.CreateDatabase(cFname, dbLangGeneral, dbVersion140)
WriteLog "Created database " & cFname & "."
'Create the tables...
WriteLog "Creating TableDefs...", 1
For Each ts In db.TableDefs
If Not StartsWith(ts.Name, "msys", "~", "$", "Name AutoCorrect") And Not EndsWith(ts.Name, "_xrep") Then
s = "SELECT "
For Each f In ts.Fields
If Not StartsWith(f.Name, "s_", "S_") Then s = s & "[" & f.Name & "], "
Next f
s = Left$(s, Len(s) - 2) & " INTO [" & ts.Name & "] IN """ & cFname & """ FROM [" & ts.Name & "];"
On Error Resume Next
db.Execute s
If Err.Number = 0 Then
WriteLog "Created [" & ts.Name & "] using " & s, 2
Else
WriteLog "Failed to create [" & ts.Name & "].", 2
WriteLog "Error " & Err.Number & ": " & Err.Description, 3
WriteLog "SQL: " & s, 3
Err.Clear
End If
tdb.TableDefs.Refresh
On Error GoTo 0
End If
Next ts
'Copy the properties...
WriteLog "Tables...", 1
For Each ts In db.TableDefs
If Not StartsWith(ts.Name, "msys", "~", "$", "Name Autocorrect") And Not EndsWith(ts.Name, "_xrep") Then
Set tt = tdb.TableDefs(ts.Name)
WriteLog ts.Name, 2
WriteLog "Table Properties...", 3
'Table properties...
For Each p In ts.Properties
On Error Resume Next
tt.Properties(p.Name) = p.value
If Err.Number = 0 Then
WriteLog p.Name & " = " & p.value, 3
Else
WriteLog "Error setting " & p.Name, 3
WriteLog Err.Number & ": " & Err.Description, 4
Err.Clear
End If
On Error GoTo 0
Next p
'Field properties...
WriteLog "Fields...", 3
For Each f In ts.Fields
If Not StartsWith(f.Name, "s_") Then
Set ft = tt.Fields(f.Name)
WriteLog f.Name, 3
WriteLog "Properties...", 3
For Each p In f.Properties
On Error Resume Next
ft.Properties(p.Name).value = p.value
Select Case Err.Number
Case 0
'Normal...
WriteLog p.Name & " = " & p.value, 4
Case cPropNotFound
'Create the property...
Dim np As Property
Set np = ft.CreateProperty(p.Name, p.Type, p.value)
ft.Properties.Append np
ft.Properties.Refresh
WriteLog "Created property " & p.Name & ", value of " & p.value, 4
Case cNotSupported, cInvalidOp
'We're not worried about these values - simply skip over them...
Case Else
WriteLog "Failed to create or change property " & p.Name & ".", 4
WriteLog "Error " & Err.Number & ": " & Err.Description, 5
Err.Clear
End Select
On Error GoTo 0
Next p
End If
Next f
'Create the indexes...
WriteLog "Table indexes...", 2
For Each i In ts.Indexes
x = False
s = "CREATE "
If i.Unique Then s = s & "UNIQUE "
s = s & "INDEX [" & i.Name & "] ON [" & ts.Name & "] ("
For Each f In i.Fields
s = s & "[" & f.Name & "], "
'Just make sure we're not dealing with replication fields...
x = StartsWith(f.Name, "s_")
Next f
'We only want
If Not x Then
WriteLog i.Name, 3
s = Left$(s, Len(s) - 2) & ") "
If i.Primary Or i.IgnoreNulls Or i.Required Then
s = s & "WITH "
If i.Primary Then s = s & "PRIMARY "
If i.IgnoreNulls Then s = s & "IGNORE NULL "
If i.Required Then s = s & "DISALLOW NULL "
End If
s = s & ";"
On Error Resume Next
tdb.Execute s
Select Case Err.Number
'Note: used select case just in case I need to add extra error numbers...
Case 0
'Normal...
WriteLog "Created index [" & i.Name & "] using " & s, 4
Case Else
WriteLog "Failed to create index [" & ts.Name & "].", 4
WriteLog "Error " & Err.Number & ": " & Err.Description, 5
WriteLog "SQL: " & s, 3
Err.Clear
End Select
On Error GoTo 0
End If
Next i
End If
Next ts
'Belt and braces tidy-up...
Set p = Nothing
Set f = Nothing
Set ft = Nothing
Set i = Nothing
Set ts = Nothing
Set tt = Nothing
tdb.Close
Set tdb = Nothing
Set db = Nothing
WriteLog "Closed database."
WriteLog "Finished.", , False
CloseLog
End Sub
总结：
索引（从 DAO 的角度来看）基本上是一种具有某些属性和字段名称及其数据类型的集合的数据结构。
它不是指向 tabledef 字段的指针的集合。
要通过 DAO 将字段添加到索引，需要一个字段对象，该对象由 CreateField() 创建。
索引对象也有一个 .CreateField() 方法，我认为这实际上是更常见的方法。
来自 http://allenbrowne.com/func-dao.html#CreateIndexesDAO :
'3. Multi-field index.
Set ind = tdf.CreateIndex("FullName")
With ind
.Fields.Append .CreateField("Surname")
.Fields.Append .CreateField("FirstName")
End With
tdf.Indexes.Append ind
请注意，this method 不采用 Type 和 Size 参数，仅采用 Name。我很乐意承认这一切有点令人困惑（或者语无伦次，如果你愿意的话）。
how does Microsoft Access know that a field created for an index fields collection associates to an equivalent field in the TableDef fields collection?
它根据名称进行检查。新索引字段的名称必须存在于 TableDef 中，并且该字段的数据类型必须是可索引的。如果不满足其中任何一个条件，您将收到一条错误消息。