Join Split Array Functions-2 ~ LEARN MS-ACCESS TIPS AND TRICKS

Continued from last week's topic.

This is the continuation of last week's Article: Join Split Array Functions

If you have not gone through the fundamentals of the above functions then please do that, by following the above link, before continuing.

Since, Join() and Split() Functions are related, It is time to try out a real-world example with them. It may not be the easiest solution to the problem we are trying to solve, but it will help to understand these Functions' usage better.

Import Employees Table from the Northwind sample database: C:\Program Files\Microsoft Office\Office11\samples\Northwind.mdb
Open a new Query in SQL View (don't select any Table from the displayed list).
Copy and paste the following SQL String into the SQL editing window and save the Query with the name EmployeeSelectQ
.
```
SELECT Employees.*
FROM Employees;
```
Design a new Form like the sample image given below (you may use the Form Wizard to quickly create the Form) using EmployeeSelectQ Query as Record Source.
Add a Text Box and a Command Button at the bottom of the design.
Select the Text Box and display the Property Sheet (View - ->Properties or Design - ->Property Sheet in 2007).
Change the Name Property Value to txtCodes.
Select the Command Button, change the Name Property value to cmdFilter, and the Caption Property value to Apply Filter.
Select the Child label of the Text Box and change its Caption value to Employee Codes:.
Display the VBA Code Module of the Form (View - ->Code or click the View Code toolbar button from the Design Menu of 2007).

Copy and paste the following VBA Code into the Form Module and save the Form with the name EmployeeSelect:

Private Sub cmdFilter_Click()
Dim txt_Codes As String, varList As Variant
Dim varCodes As Variant, j As Integer, x
Dim maxCodes As Variant, invalid_Codes As String

txt_Codes = Nz(Me.txtCodes, "")
maxCodes = DMax("EmployeeID", "Employees")

If Len(txt_Codes) = 0 Then
  varList = Null
Else
   'Split the items into the array.
  
  '(Here Array() Function will not work
  'becuase the values in txtCodes variable is a String
  'and will be treated as a single item).

  varCodes = Split(txt_Codes, ",")
  
  'Validation check
  invalid_Codes = ""
  For j = 0 To UBound(varCodes)
     x = Val(varCodes(j))
     If x < 1 Or x > maxCodes Then
        invalid_Codes = invalid_Codes & Format(x, "0 ")
     End If
  Next
  If Len(invalid_Codes) > 0 Then
     MsgBox "Invalid Employee Codes: " & invalid_Codes & vbCr & vbCr & "Correct and retry."
     Exit Sub
  End If
  'here "varList = txt_Codes" is also works
  'because txt_Codes values are separated with commas already
  varList = Join(varCodes, ",")
End If

  'Call the EmployeeFilter() function
  EmployeeFilter varList
  Me.RecordSource = "EmployeeSelectQ"
  Me.Requery

End Sub

Press Alt+F11 to open the VBA Editing window, if you have already closed it, select Module from Insert Menu to add a new Standard Module.

Copy and paste the following VBA Code of EmployeeFilter() Function into the Standard Module and save it:

Public Function EmployeeFilter(ByVal Criteria As Variant)
Dim strsql0 As String, sql As String
Dim db As Database, qryDef As QueryDef

strsql0 = "SELECT Employees.* FROM Employees WHERE (((Employees.EmployeeID) In ("

Set db = CurrentDb
Set qryDef = db.QueryDefs("EmployeeSelectQ")

If IsNull(Criteria) Or Len(Criteria) = 0 Then
    sql = "SELECT Employees.* FROM Employees;"
Else
    Criteria = Criteria & ")));"
    sql = strsql0 & Criteria

End If
    qryDef.SQL = sql
    db.QueryDefs.Refresh

End Function

Open the EmployeeSelect Form in a normal view. The sample image of the Form is given below:
Enter the Employee IDs 2,3,7 and click on the Apply Filter Command Button.

Now, the EmployeeSelect Form has only three records, with employee codes 2,3 & 7.
Delete all the Text Box contents and click on the Apply Filter Command Button.

The filter action is now reversed and all the records of the Employee Table are now available on the Form. In other words, it works like a Reset command when the TextBox is empty.

You may try, with some different Employee IDs list.

The values entered into the TextBox must be within the range of the available Employee Code. The numbers entered outside this range will display an Error message and abort the program.