# Normalizing data in Excel table column with multiple values

I have a table in excel which has 11 columns and 50,000 rows of data.

One of the columns contains email addresses and in some instances multiple addresses, separated with a ; character. Eg. a cell in that column might look like a@gmail.com;b@gmail.com;x@gmail.com .

In those instances where I have multiple addresses, I need to delete the row with the multiple addresses and create new rows in the table with each one of those addresses, also copying and pasting the rest of the columns.

An example of how originally the data might look like and how it should look like after processing:

Before:

After:

In order to accomplish that I wrote this piece of code:

Sub Fix_Table()
i = 1
table_size = Range("Table1").Rows.Count
'Goes through Table1 in "To" column and fixes the recipients
Do While i <= table_size

cell_value = Range("Table1[To]")(i)

If InStr(Range("Table1[To]")(i), ";") Then
from_table = Range("Table1[From]")(i)
subject_table = Range("Table1[Subject]")(i)
infolder_table = Range("Table1[In_Folder]")(i)
size_table = Range("Table1[Size]")(i)
weekday_table = Range("Table1[Weekday]")(i)
date_table = Range("Table1[Date]")(i)
month_table = Range("Table1[Month]")(i)
year_table = Range("Table1[Year]")(i)
time_table = Range("Table1[Time]")(i)
inout_table = Range("Table1[In/out]")(i)

recipients_table = Split(cell_value, ";")
number_of_recipients = UBound(recipients_table, 1) - LBound(recipients_table, 1)
Range("Table1[To]")(i).EntireRow.Delete

For k = 1 To number_of_recipients + 1
Range("Table1[To]")(i).EntireRow.Insert
Range("Table1[From]")(i) = from_table
Range("Table1[Subject]")(i) = subject_table
Range("Table1[In_Folder]")(i) = infolder_table
Range("Table1[Size]")(i) = size_table
Range("Table1[Weekday]")(i) = weekday_table
Range("Table1[Date]")(i) = date_table
Range("Table1[Month]")(i) = month_table
Range("Table1[Year]")(i) = year_table
Range("Table1[Time]")(i) = time_table
Range("Table1[In/out]")(i) = inout_table
Range("Table1[To]")(i) = recipients_table(k - 1)
i = i + 1
table_size = table_size + 1
Next k

Else
i = i + 1
End If

Loop
End Sub


The above code works , however it is extremely slow! Is there any faster way that I could do that for that size of data?

• I see someone on your [now deleted] SO question mentioned switching off Application.ScreenUpdating and Application.Calculation to speed up the processing - while somewhat useful, note that this recommendation doesn't make your code/logic any more efficient. Glad you took your question over here - you'll learn a ton of things Stack Overflow wouldn't bother showing you =) – Mathieu Guindon Aug 21 '17 at 14:50
• How important is it to -insert- the new rows in place? Can they be added onto the end of the data? Would re-sorting to match the original order be necessary? – PeterT Aug 21 '17 at 16:58
• Its not important as long as they are in the table. They dont need to be sorted out , this is just data that i later feed into a pivot chart to get some analytics. – Dimitrios Papadopoulos Aug 22 '17 at 7:01

Ok, so this ended up being a little bit longer/more complicated than I hoped. I will do my best to explain so that you can follow along. Please ask questions if you get lost or confused!

Code first, then explanations:

Option Explicit

Private Type TRecord
To As String
From As String
Subject As String
InFolder As String
Size As String
Weekday As String
RecordDate As Date
Month As String
Year As String
Time As String
InOut As String
End Type

Sub New_Fix_Table()
' Be sure to add 'Option Explicit' at the top of your modules. This prevents undeclared variables from slipping through.

' Never use underscores in names. They have special meaning to the interpreter.
' table_size = Range("Table1").Rows.Count

' ## Not Needed due to UBound/LBound ##
' Dim tableSize As Long
' Be sure to also properly qualify you range references.
' TableSize = ActiveWorkbook.Range("Table1").Rows.Count - Without proper qualification, your Range is really ActiveWorkbook.Range
' tableSize = ThisWorkbook.Range("Table1").Rows.Count
' ## ##

'Goes through Table1 in "To" column and fixes the recipients

Dim i As Long

' For loops such as these, I prefer for loops
' Do While i <= table_size

' I strongly prefer arrays for this purpose. If it was my own project, I even would use classes, but one step at a time for now.

' Change this to point to the correct worksheet.
Dim inputSheet As Worksheet
Set inputSheet = ThisWorkbook.Worksheets("TargetSheet")

' If your data is in a table, then you can use this method instead of referring to the range.
Dim tableData As Variant
tableData = inputSheet.ListObjects(1).Range.value

' Now, here is a trick I use when processing table data in a much more efficient manner.
' This does require a reference to Microsoft Scripting Runtime

' Now we have a dictionary where we can use a key and return the index position of that key

' This is where it gets a little bit tricky. If we encounter a row with multiple emails, we need to duplicate the records.
' Otherwise, we want to keep the records as is. For this task, collections to the rescue!

' Having declared a Record Type, I can now use the Type as a container for my data (without needing a class)
Dim record As TRecord

' The records collection will contain the created records
Dim records As Collection
Set records = New Collection

Dim i As Long
' We loop through arrays using LBound and Ubound (lower bound, upper bound). The '1' denotes rows, whereas '2' would denote columns.
' I add 1 to the lower bound so I can skip the header row.
For i = LBound(tableData, 1) + 1 To UBound(tableData, 1)
' Set all the properties of the record.

' Split the addresses. If there are multiple addresses we dont need to rewrite the record, we just need to adjust the To field.
If InStr(tableData(i, headerIndices("To")), ";") > 0 Then

Dim j As Long
End If
Next
Else
End If
Next

' Now we have a colleciton of all of the records we need. Now, we need to translate those back into an array.
Dim outputData As Variant

' The row is 0 based so we can add headers, but the headerIndices dictionary is already 1-based, so we leave the columns 1 based.
' Admittedly, I would avoid a mis-match of bases for re-dimming an array, I am only doing it this way to prevent confusion.
ReDim outputData(0 To records.Count, 1 To headerIndices.Count)

' An array with the same base-dimensions would be one of the two following:
' ReDim outputData(0 To records.Count, 0 To headerIndices.Count - 1)
' ReDim outputData(1 To records.Count + 1, 1 To headerIndices.Count)
' You would then need to adjust the actual filling of the array as well.

i = LBound(outputData, 2)

' Loop through all of the stored headers
' The LBound here dynamically points to the header row.
Next

' This way we can dynamically fill in the array.

i = LBound(outputData, 2) + 1
For Each record In records
Next

' Now we just have to put the output data somewhere. Let's reuse the sheet we pulled from.
OutputArray outputData, inputSheet, "Output_Data"
End Sub

Public Function GetHeaderIndices(ByVal InputData As Variant) As Scripting.Dictionary
If IsEmpty(InputData) Then Exit Function

Dim i As Long
For i = LBound(InputData, 2) To UBound(InputData, 2)
If Not headerIndices.Exists(Trim(InputData(LBound(InputData, 1), i))) Then _
Next

End Function

Public Sub OutputArray(ByVal InputArray As Variant, ByVal InputWorksheet As Worksheet, ByVal TableName As String)

If NumberOfArrayDimensions(InputArray) = 2 Then
If LBound(InputArray, 1) = 0 Then AddLengthH = 1
If LBound(InputArray, 2) = 0 Then AddLengthW = 1

Dim r As Range
If Not InputWorksheet Is Nothing Then
With InputWorksheet
.Cells.Clear
r.value = InputArray
.ListObjects.Add(xlSrcRange, r, , xlYes).Name = TableName

With .ListObjects(1).Sort
.MatchCase = False
.Orientation = xlTopToBottom
.SortMethod = xlPinYin
.Apply
End With
End With
End If
End If
End Sub


## Initial Notes

The first thing that struck me about your code was that you literally have no variable declarations. Lines like :

cell_value = ...


Are pretty much the same as :

Dim cell_value as Variant
cell_value = ...


The only difference between the two is that the second is at least explicit about wanting a variant. The first is implicit.

First bit of advice avoid implicit commands as much as possible. The reason for this is quite simple, there is a tendency to think that the computer is magically doing something it shouldnt be, but really you told it to do exactly what it is doing and as a result, you have a bug that can be nearly invisible.

Consider for example :

myRange = Range("SomeRange")


This declares a myRange (which the reader expects to be a Range) and converts the range to an array. This in itself is confusing, but, even worse, I can still do :

Set myRange = Range("SomeRange")


And it is now a range reference (the only difference being the Set keyword). While it is easy to read the code and determine what is happening for us, you will inevitably lose a bug in there that you will have to search for.

Option Explicit to the Rescue!

Option Explicit is one of the best things in VBA. It is truly simple, but it makes the simplest of bugs super simple to prevent (and even simpler to find). With Option Explicit at the top of a module, the compiler will throw an error when a variable isnt declared.

' This won't compile. Note the minor (but potentially difficult to find) spelling error between Very and Vary.
Dim SomeVeryLongVariableName as Long
SomeVaryLongVariableName = 10


To make Option Explicit a breeze to use:

1. Open the Developer Window
2. Press CTRL+T and then CTRL+O.
3. Check the box for Require Variable Declaration.
4. While you're in there, I recommend going to the general tab and selecting Break in Class Module under error trapping.

Qualifying References

One of the most common mistakes someone new to VBA will make is doing:

SomeVariable = Range("SomeRange")

' or

SomeVariable = Range("SomeRange").Value


There are two problems with the first version. The problem that is solved by the second version is that we specify the property we are accessing. The default property of a Range is .Value so we don't need .Value, but it is discouraged to implicitly access .Value.

The second issue is that we rely implicitly on ActiveSheet.Range("SomeRange"). This is a silent killer. I refuse to work with the Active Anything unless I absolutely must and even then, I prefer not to. It is always best to specifically call the object you are working with.

' This is literally better than not using a worksheet reference at all
Dim Foo as Worksheet
Set Foo = ActiveSheet

...many lines later...

DoSomething Foo


Why is this little change better? It is using the active sheet! While not ideal, it at least ensures that Foo points to the same worksheet unless we explicitly change the worksheet it is pointing to. It is stronger than the ActiveSheet reference.

Even better would be:

Dim Foo as Worksheet
Set Foo = ThisWorkbook.WorkSheets("SomeFoo")


The ThisWorkbook object is the workbook that is running the code, and by using a string argument as a call to the collection we can return the specific worksheet back.

Working on the Worksheet

Now lets get into the meat of the problem. Your code is slow because you are operating on the worksheet. Its that simple. A hundred calls to the Worksheet.Range will be slower than a hundred calls to Data(x, y). An array is faster, and is easier to use.

Even worse is when you not only access the cells by a range reference, but when you do :

EntireRow.Delete


Now you've really upset the worksheet. It has to update calculations, it has to resize stuff, fix formatting (if in a table), check number formatting, etc. It is a costly operation. If you're deleting a lot of rows...avoid it at all cost.

Enter the world of arrays. Not only are they fast but they are easy. Worksheet.Cells(1, 1) becomes Data(1, 1). Once you load in the data to the array (Data) you can manipulate, access, delete the values all you want. The worksheet doesn't care. It doesnt see what is happening to the same data it was previously responsible for.

## Putting It Together

I am not going to go through the code line by line, particularly because I already provided in-line comments to help make the code a bit easier to read. This will be a broad explanation of what the code does.

1. First, it loads in all the data from a ListObject (excel Table) into an array. That's the easy part.
2. Once we have the data, we need to know the indices of the headers. This makes manipulating the data much easier. It also allows you to move columns around all you want without breaking the code (just ensure the names are still there).
3. Using a custom Type we can store all of the data in a defined structure. A Type is similar to a Struct in other languages. In essence, it is a variable that has properties, but that isnt an object. Thus, it cannot be New'ed up.
4. Loop through all of the rows, and create new records for cells with multiple addresses. Since the Type cannot be New'ed, it will retain old values. This means we dont need to re-create the entire record for each new row. We just need to change the new values, then add it to the collection.
5. Once the collection is loaded with records, we can translate them into a new array that is appropriately sized. No need to add/remove rows. It is just the right size at creation.
6. The OutputArray method will take an array and a worksheet and it will clear the cells on that worksheet, put the array onto the worksheet, and then turn that output into a table. Point it where you want the output to go, and it will do the rest.

I didn't test the code on my end (I didnt want to bother creating a test table), but I imagine it should run in a matter of seconds.

Note : Microsoft Scripting Runtime To use the code as is, you will need to add a reference to the Microsoft Scripting Runtime Library. There are plenty of resources for adding references, but ask if you get lost.

## RubberDuck. Use It. Love It. Prof-It

I tend to be shameless about my plugs for Rubberduck, largely because the head of the tool, Mat's Mug, is unabashed in his attempts to convert everyone on SO to using RD. That said, it is an amazing tool, especially for beginners, and it would make most of the above comments stupidly easy to implement. Honestly, it would.

Check it out here: http://rubberduckvba.com/.

## Wrapping Up

Let me know how the code above works for you, and do your best to use it as an example for future projects. If you manage to implement even half of those suggestions you'll save yourself potentially months of costly learning experiences through failed projects. Best of luck!

EDIT: Use this code instead to fix the error from above. The error is caused by adding a custom-type to a collection (I have never used Types outside of a class before so I didn't think of the error in advance). This approach is slightly more advanced, but it shouldnt be too complex.

In a Class Module named 'Record'

Option Explicit

Private Type TRecord
ToField As String
FromField As String
Subject As String
InFolder As String
Size As String
WeekDay As String
RecordDate As Date
Month As String
Year As String
Time As String
InOut As String
End Type

Private this As TRecord

Public Property Get ToField() As String
ToField = this.ToField
End Property
Public Property Get FromField() As String
FromField = this.FromField
End Property
Public Property Get Subject() As String
Subject = this.Subject
End Property
Public Property Get ReceivedDate() As Date
End Property
Public Property Get InFolder() As String
InFolder = this.InFolder
End Property
Public Property Get Size() As String
Size = this.Size
End Property
Public Property Get WeekDay() As String
WeekDay = this.WeekDay
End Property
Public Property Get RecordDate() As Date
RecordDate = this.RecordDate
End Property
Public Property Get Month() As String
Month = this.Month
End Property
Public Property Get Year() As String
Year = this.Year
End Property
Public Property Get Time() As String
Time = this.Time
End Property
Public Property Get InOut() As String
InOut = this.InOut
End Property

Public Property Let ToField(value As String)
this.ToField = value
End Property
Public Property Let FromField(value As String)
this.FromField = value
End Property
Public Property Let Subject(value As String)
this.Subject = value
End Property
Public Property Let ReceivedDate(value As Date)
End Property
Public Property Let InFolder(value As String)
this.InFolder = value
End Property
Public Property Let Size(value As String)
this.Size = value
End Property
Public Property Let WeekDay(value As String)
this.WeekDay = value
End Property
Public Property Let RecordDate(value As Date)
this.RecordDate = value
End Property
Public Property Let Month(value As String)
this.Month = value
End Property
Public Property Let Year(value As String)
this.Year = value
End Property
Public Property Let Time(value As String)
this.Time = value
End Property
Public Property Let InOut(value As String)
this.InOut = value
End Property


This class uses a code pattern I learned from Mat's Mug. Declare the Type for the class as a Private Type, then declare a private this that refers to that type. As a result, you have an organized Type to hold your variables, and you get intellisense.

Once you do that, you just need to open up the property accessors. In this case, I made everything public. This isnt good practice, but I am avoiding teaching you too much at once (I would prefer not to use a class as is, but it is the best approach at this point).

This Code Goes in Your Module

Option Explicit

Sub New_Fix_Table()
' Be sure to add 'Option Explicit' at the top of your modules. This prevents undeclared variables from slipping through.

' Never use underscores in names. They have special meaning to the interpreter.
' table_size = Range("Table1").Rows.Count

' ## Not Needed due to UBound/LBound ##
' Dim tableSize As Long
' Be sure to also properly qualify you range references.
' TableSize = ActiveWorkbook.Range("Table1").Rows.Count - Without proper qualification, your Range is really ActiveWorkbook.Range
' tableSize = ThisWorkbook.Range("Table1").Rows.Count
' ## ##

'Goes through Table1 in "To" column and fixes the recipients

' For loops such as these, I prefer for loops
' Do While i <= table_size

' I strongly prefer arrays for this purpose. If it was my own project, I even would use classes, but one step at a time for now.

' Change this to point to the correct worksheet.
Dim inputSheet As Worksheet
Set inputSheet = ThisWorkbook.Worksheets("TargetSheet")

' If your data is in a table, then you can use this method instead of referring to the range.
Dim tableData As Variant
tableData = inputSheet.ListObjects(1).Range.value

' Now, here is a trick I use when processing table data in a much more efficient manner.
' This does require a reference to Microsoft Scripting Runtime

' Now we have a dictionary where we can use a key and return the index position of that key

' This is where it gets a little bit tricky. If we encounter a row with multiple emails, we need to duplicate the records.
' Otherwise, we want to keep the records as is. For this task, collections to the rescue!

' Having declared a Record Type, I can now use the Type as a container for my data (without needing a class)
Dim initialRecord As record

' The records collection will contain the created records
Dim records As Collection
Set records = New Collection

Dim i As Long
' We loop through arrays using LBound and Ubound (lower bound, upper bound). The '1' denotes rows, whereas '2' would denote columns.
' I add 1 to the lower bound so I can skip the header row.
For i = LBound(tableData, 1) + 1 To UBound(tableData, 1)
Set initialRecord = New record
' Set all the properties of the record.

' Split the addresses. If there are multiple addresses we dont need to rewrite the record, we just need to adjust the To field.
If InStr(tableData(i, headerIndices("To")), ";") > 0 Then

Dim j As Long
Dim splitRecord As record
Set splitRecord = New record
' Because of how objects are passed around, you cant copy a class through assignment. You must duplicate the properties manually into a new class.
splitRecord.FromField = initialRecord.FromField
splitRecord.Subject = initialRecord.Subject
splitRecord.InFolder = initialRecord.InFolder
splitRecord.Size = initialRecord.Size
splitRecord.WeekDay = initialRecord.WeekDay
splitRecord.RecordDate = initialRecord.RecordDate
splitRecord.Month = initialRecord.Month
splitRecord.Year = initialRecord.Year
splitRecord.Time = initialRecord.Time
splitRecord.InOut = initialRecord.InOut

End If
Next
Else
End If
Next

' Now we have a colleciton of all of the records we need. Now, we need to translate those back into an array.
Dim outputData As Variant

' The row is 0 based so we can add headers, but the headerIndices dictionary is already 1-based, so we leave the columns 1 based.
' Admittedly, I would avoid a mis-match of bases for re-dimming an array, I am only doing it this way to prevent confusion.
ReDim outputData(0 To records.Count, 1 To headerIndices.Count)

' An array with the same base-dimensions would be one of the two following:
' ReDim outputData(0 To records.Count, 0 To headerIndices.Count - 1)
' ReDim outputData(1 To records.Count + 1, 1 To headerIndices.Count)
' You would then need to adjust the actual filling of the array as well.

i = LBound(outputData, 2)

' Loop through all of the stored headers
' The LBound here dynamically points to the header row.
Next

' This way we can dynamically fill in the array.

i = LBound(outputData, 2) + 1

Dim outputRecord As record
For Each initialRecord In records
Next

' Now we just have to put the output data somewhere. Let's reuse the sheet we pulled from.
OutputArray outputData, inputSheet, "Output_Data"
End Sub

Public Function GetHeaderIndices(ByVal InputData As Variant) As Scripting.Dictionary
If IsEmpty(InputData) Then Exit Function

Dim i As Long
For i = LBound(InputData, 2) To UBound(InputData, 2)
If Not headerIndices.Exists(Trim(InputData(LBound(InputData, 1), i))) Then _
Next

End Function

Public Sub OutputArray(ByVal InputArray As Variant, ByVal InputWorksheet As Worksheet, ByVal TableName As String)

If NumberOfArrayDimensions(InputArray) = 2 Then
If LBound(InputArray, 1) = 0 Then AddLengthH = 1
If LBound(InputArray, 2) = 0 Then AddLengthW = 1

Dim r As Range
If Not InputWorksheet Is Nothing Then
With InputWorksheet
.Cells.Clear
r.value = InputArray
.ListObjects.Add(xlSrcRange, r, , xlYes).Name = TableName

With .ListObjects(1).Sort
.MatchCase = False
.Orientation = xlTopToBottom
.SortMethod = xlPinYin
.Apply
End With
End With
End If
End If
End Sub


The only main difference is that now we are using an object instead of a type, and we must manually copy the object any time we want to create a new one (whereas, with the Type, we just changed the To field).

• +1 for RubberDuck. I have been assimilated. – PeterT Aug 21 '17 at 19:26
• Hi Brandon and thank you for your answer. Unfortunately there are indeed some tricky parts that are difficult to understand , but for the most part i get what you are saying. For starters i am trying to make the code actually run and then take it step by step to see how it actually works. I am getting a compile error "Only user-defined typed defined in public object modules can be coerced to or from a variant or passed to late-bound functions" on the records.Add record. Any idea there? – Dimitrios Papadopoulos Aug 22 '17 at 7:12
• @DimitriosPapadopoulos See the edits. I hadnt used Types in a collection before so I didnt know that they werent compatible. This does mean that we have to resort to using a class, so it may become a bit more difficult to follow. Take your time in understanding the code. Once you make sense of classes they will change everything. – Brandon Barney Aug 22 '17 at 12:02
• @BrandonBarney if i pass all my data from the worksheet into an array and work with that array (instead of working in the actual worksheet) and in the end just output everything in a new worksheet would that make the process faster? I ll accept your answer and thanks a lot for it , i learned a lot of things , although i still can't practically use it a) because i still get errors and most importantly because b) i ll need to make future changes and its important for me to understand the code 100% and all this is somehow "too" complicated. – Dimitrios Papadopoulos Aug 23 '17 at 12:26
• @DimitriosPapadopoulos Yes that is correct. Arrays are much faster, and that is the majority of where the improvement in speed comes from. The rest is just a framework for using the arrays and splitting the rows. As long as you can get by with your own process for those bits, you will be fine for the short term. Definitely take some time to learn about dictionaries and classes though. Doing so will make the process much easier for you. – Brandon Barney Aug 23 '17 at 13:41

So I had a similar problem recently, dealing with a "database" of records where I needed to add and update records. I was stuck with these constraints:

• Using memory-based array is MUCH faster than working with data directly on the worksheet
• That's all very nice until you need to ADD a row to that array. This is forbidden by Excel because when you attempt to ReDim, you're only allowed to adjust the second dimension. Adding rows only affects the first dimension.

My solution ended up building a class that handles all my "database" interactions. I've taken excerpts from that code to show an example in this post. (My requirements we somewhat different and involved creating a unique key with a Dictionary for my DatabaseHandler class. I can post that code in another review, if anyone's interested.)

The basic idea of the solution is:

1. Determine the Range of the data on the worksheet ==> Rows by Cols
2. Add an arbitrary "buffer" zone of rows to expand the range ==> Rows+buffer by Cols
3. Copy the expanded range into the memory-based array
4. Add rows into the empty rows of the array as needed
5. If the added row is at the end of the array, flip the memory-based array back to the worksheet, then re-size and re-copy the Range back into the array. The trick for speed is to manage the size of the extra buffer.

Using this technique, I was able to process your data set on 99,000 rows in 25 seconds.

To size the range and copy to an array, my example uses the following routine:

Private Sub BuildDataArray(ByRef ws As Worksheet, _
ByRef arr As Variant, _
ByRef lastR As Long, _
ByRef lastC As Long)

'--- we'll copy all the data on the database worksheet into a memory-based
'    array, but we'll also add a buffer of extra empty rows. these empty
'    rows allows multiple ADDs to the database without constantly resizing
'    (ReDim-ing)
Const DATA_BUFFER As Long = 5000
Dim dbRange As Range
With ws
lastR = .Cells(.Cells.Rows.count, 1).End(xlUp).Row
lastC = .Cells(1, .Cells.Columns.count).End(xlToLeft).Column
'--- set up the range, but skip the header row
Set dbRange = .Range(.Cells(2, 1), .Cells(lastR, lastC))
'--- and create the memory array
arr = .Range(.Cells(2, 1), .Cells(lastR + DATA_BUFFER, lastC))
End With
End Sub


Since the parameters are passed by reference (ByRef), the results can be used by the caller. Likewise the routine to copy the array back to the worksheet is:

Private Sub CommitData(ByRef ws As Worksheet, _
ByRef arr As Variant)

With ws
.Range(.Cells(2, 1), .Cells(UBound(arr, 1), UBound(arr, 2))) = arr
End With
End Sub


The main process simply loops through the data in the array and when it encounters a row with multiple emails in the "to" field, it creates extra rows at the end of the existing data (in the empty part of the array). The trick is to detect when the memory array is full.

Public Sub SeparateEmails()
Dim dbWorkbook As Workbook
Dim dbWorksheet As Worksheet
Dim lastRow As Long
Dim lastCol As Long
Dim dataArray As Variant

Set dbWorkbook = ThisWorkbook
Set dbWorksheet = dbWorkbook.Sheets("Sheet1")

BuildDataArray dbWorksheet, dataArray, lastRow, lastCol

Dim i As Long
Dim j As Long
Dim k As Long
For i = 1 To lastRow
emailAddrs = Split(dataArray(i, 3), ";", , vbTextCompare)
'--- replace the email list with only the first email address
'    then add new rows to the end
For j = 1 To UBound(emailAddrs)
'--- copy all the columns
For k = 1 To lastCol
Next k
'--- now copy over the email field with the single value

'--- increment the row index for added rows, but check
'    against the buffer limit and increase as needed
If lastAddedRow = UBound(dataArray, 1) Then
CommitData dbWorksheet, dataArray
BuildDataArray dbWorksheet, dataArray, lastRow, lastCol
End If
Next j
End If
Next i
CommitData dbWorksheet, dataArray
End Sub


I haven't come up with a set of measurements/timing on different size data sets. But basically if you can gauge the size of your original data and how much you think it may grow, you can estimate the buffer size to use. You're looking for a balance in how often you perform read/writes to the worksheet versus available memory and efficiency.

As a bonus, I've added the timing code from this excellent answer so you can perform your own measurements. Here's the whole thing:

Option Explicit

Private Declare Function getFrequency Lib "kernel32" _
Alias "QueryPerformanceFrequency" (cyFrequency As Currency) As Long
Private Declare Function getTickCount Lib "kernel32" _
Alias "QueryPerformanceCounter" (cyTickCount As Currency) As Long

Sub test()
Application.ScreenUpdating = False
Dim startTimer As Double
Dim endTimer As Double
startTimer = MicroTimer
SeparateEmails
endTimer = MicroTimer
Debug.Print "elapsed time = " & Format(endTimer - startTimer, "0.00000 secs")
Application.ScreenUpdating = False
End Sub

Public Sub SeparateEmails()
Dim dbWorkbook As Workbook
Dim dbWorksheet As Worksheet
Dim lastRow As Long
Dim lastCol As Long
Dim dataArray As Variant

Set dbWorkbook = ThisWorkbook
Set dbWorksheet = dbWorkbook.Sheets("Sheet1")

BuildDataArray dbWorksheet, dataArray, lastRow, lastCol

Dim i As Long
Dim j As Long
Dim k As Long
For i = 1 To lastRow
emailAddrs = Split(dataArray(i, 3), ";", , vbTextCompare)
'--- replace the email list with only the first email address
'    then add new rows to the end
For j = 1 To UBound(emailAddrs)
'--- copy all the columns
For k = 1 To lastCol
Next k
'--- now copy over the email field with the single value

'--- increment the row index for added rows, but check
'    against the buffer limit and increase as needed
If lastAddedRow = UBound(dataArray, 1) Then
CommitData dbWorksheet, dataArray
BuildDataArray dbWorksheet, dataArray, lastRow, lastCol
End If
Next j
End If
Next i
CommitData dbWorksheet, dataArray
End Sub

Private Sub BuildDataArray(ByRef ws As Worksheet, _
ByRef arr As Variant, _
ByRef lastR As Long, _
ByRef lastC As Long)

'--- we'll copy all the data on the database worksheet into a memory-based
'    array, but we'll also add a buffer of extra empty rows. these empty
'    rows allows multiple ADDs to the database without constantly resizing
'    (ReDim-ing)
Const DATA_BUFFER As Long = 5000
Dim dbRange As Range
With ws
lastR = .Cells(.Cells.Rows.count, 1).End(xlUp).Row
lastC = .Cells(1, .Cells.Columns.count).End(xlToLeft).Column
'--- set up the range, but skip the header row
Set dbRange = .Range(.Cells(2, 1), .Cells(lastR, lastC))
'--- and create the memory array
arr = .Range(.Cells(2, 1), .Cells(lastR + DATA_BUFFER, lastC))
End With
End Sub

Private Sub CommitData(ByRef ws As Worksheet, _
ByRef arr As Variant)

With ws
.Range(.Cells(2, 1), .Cells(UBound(arr, 1), UBound(arr, 2))) = arr
End With
End Sub

Function MicroTimer() As Double
'Returns seconds.
Dim cyTicks1 As Currency
Static cyFrequency As Currency
MicroTimer = 0
' Get frequency.
If cyFrequency = 0 Then getFrequency cyFrequency
' Get ticks.
getTickCount cyTicks1
' Seconds
If cyFrequency Then MicroTimer = cyTicks1 / cyFrequency
End Function

• Why use a buffer array at all? I have a project that can pull n rows of data, and it is basically impossible to guess how many rows there will be, and how many will remain. Classes and collections make it stupidly simple to maintain though. I recommend having a AnonymousRecord class where there is Dictionary (Header, Value), GetPropertyByName(Header), SetPropertyByName(Header). Build another class that converts the table into a collection of records and you'll never look back. – Brandon Barney Aug 21 '17 at 19:30
• FWIW the answer I posted uses a similar approach, it just defines the structure of the container beforehand. Not ideal, but given that OP doesnt have his variables declared I wasnt going to jump into the intermediate-advanced stuff. – Brandon Barney Aug 21 '17 at 19:31
• I had to step away too many times while typing in my answer, and so unfortunately didn't get to see yours before I posted mine. Yours is an excellent answer and you make a good point with your Collections and Dictionaries. My own class holds the data in an array to blit back and forth to the worksheet easily, but the real access to all the data used a Dictionary as the hash to access any specific record. I believe we're probably talking similar approaches here, but i can always learn. – PeterT Aug 21 '17 at 19:35
• No problem at all, certainly not bashing on your answer :). Just a suggestion. When I learned how to use collections and classes for this I was blown away (and I managed to do things I thought impossible). The idea of a buffer array isnt a bad one, but there is an innate inefficiency since you are always either checking the size, resizing, or you are allocating memory that wont be used (resized too large). If you can manage to work with an object that is dynamic in size you can save a lot of operations :). – Brandon Barney Aug 21 '17 at 19:44

I won't give a long answer with lots of comments, but if you want to simply separate out the emails and replace contents of a table, then I would suggest that this will be very fast:

A few seconds for 97K rows...

Public Function paintRows(ByRef arr As Variant, _
ByRef newArr As Variant, _
ByVal arrRow As Long, _
ByVal currentRow As Long, _
ByVal colToSplit As Long, _
splitArr As Variant) As Long

Dim newRows As Long, paint As Long, n As Long, ind As Long
newRows = (UBound(splitArr) + 1)

For n = LBound(arr, 2) To UBound(arr, 2)
For paint = arrRow To arrRow + newRows - 1
ind = (paint - arrRow) Mod newRows
If n = colToSplit Then
newArr(paint, n) = Trim(splitArr(ind))
Else
newArr(paint, n) = arr(currentRow, n)
End If
Next paint
Next n
paintRows = newRows
End Function

Public Sub splitRowsResize()

Application.ScreenUpdating = False

Const delim = ";"

Dim r As Range
Set r = Sheet4.ListObjects("Table1").DataBodyRange  'define your table data range correctly

Dim rcc As Long, m As Long
m = 10 ^ 6
rcc = r.Columns.count
ReDim arr(1 To m, 1 To r.Columns.count)

Dim a As Variant, arrVals As Variant
arrVals = r.Value

Dim i As Long, j As Long, arrRow As Long
arrRow = 1
j = 3  'here column 3 is 'To' emails - adjust as necessary
For i = LBound(arrVals) To UBound(arrVals)
a = Split(arrVals(i, 3), delim)
arrRow = arrRow + paintRows(arrVals, arr, arrRow, i, j, a)
Next i

Dim topLeft As Range    'where you will output your database version
Set topLeft = r.Cells(1, 1)

topLeft.Resize(arrRow - 1, rcc) = arr

Application.ScreenUpdating = True
End Sub