Category Archives: Access

A simple method for linking and viewing images in Access

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Access has traditionally not been a good environment for storing media, images and files due to database bloating. Because of that many people prefer to store images in the file system and link to those files from Access. The approach shown below is just one of many methods, and has these features:

  • Files are stored in a predefined directory
  • The images are located / stored using a button on a subform. They are displayed in an unbound image frame on the main form.
  • The same button is used to browse for and display a new image, and to display an existing image.
  • Images are located on disk using the FileDialog object. Once selected you can open, save, rename or otherwise modify the file.

You will need to set up the following to use this code:

  • A command button on a subform, with the code shown in Listing 1.
  • A text field in the subform, named Photo
  • An unbound image frame in the main form, called imgDisplay. When you set up this control you will be prompted to browse for an image. Whatever you select will become the default image.
  • You will also need to save Listing 2 in the code module of the subform.

Listing 1

TryAgain:
    If IsNull(Me.Photo) Or Len(Me.Photo) = 0 Then
        'no image; load an image before showing
        CopyImage
        GoTo TryAgain
    Else
        Me.Parent!imgDisplay.Picture = Me.Photo
    End If

The If statement checks first to see whether the Photo field is empty. If it is the CopyImage function launches, prompting the user to locate an image for the record. Once the image is copied and the link written, the code returns to the top of the routine and loads the link into the image container.

Listing 2

Private Function CopyImage()
    ''====================================================
    ''You will need a reference to the Microsoft Office x.0 Object Library
    '' where x = 10,11,12 or 13
    ''====================================================

    Dim fd As Office.FileDialog
    Const SAVE_PATH = "H:\Documents\Images\" 'default folder for saving the images
    Dim strFname As String
    Dim i As Integer
    Dim vrtSelectedItem As Variant
    
    Set fd = Application.FileDialog(msoFileDialogFilePicker)
    
    With fd
        .Filters.Clear
        
        .Filters.Add "All files", "*.*"
        .Filters.Add "Images", "*.gif; *.jpg; *.jpeg", 1
        .AllowMultiSelect = False
        
        If .Show = -1 Then
            For Each vrtSelectedItem In .SelectedItems
                strFname = ""
                For i = Len(vrtSelectedItem) To 1 Step -1
                    If Mid(vrtSelectedItem, i, 1) = "\" Then
                        strFname = Mid(vrtSelectedItem, i + 1)
                        Exit For
                    End If
                Next i
                'copy to the destination directory
                FileCopy vrtSelectedItem, SAVE_PATH & strFname
                ‘optional: delete the original, keeping only the copy.
                Kill vrtselecteditem
                ‘write the full path to the Photo field
                Me.Photo = SAVE_PATH & strFname
            Next vrtSelectedItem
            'The user pressed Cancel.
            Else
        End If
    End With
    
    'Set the object variable to Nothing.
    Set fd = Nothing
End Function

Regional settings cause report to fail in Access

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Here’s a weird problem that I encountered recently. In a database that I had developed for a client, one of the reports refused to run when they switched their regional settings to another language — a problem, since some of the users were German and hence would be unable to use the report without changing back to English settings first.

The problem came down to the headers that I had used in the crosstab query that fed the report. It had text strings like “01_Mon”, “02_Tue”, etc for a total of 10 headers. And of course, these became fields for the report.

What I hadn’t realised what that Access interpreted these as dates, so when the regional settings changed, they became “01_Mo”, 02_Di”, etc … and the report broke. The fix was simple: use generic “Day_01”, “Day_02”, etc as the day headers, and update the report controls to read from these generic fields.

I guess it’s another case of crosstab queries and reports having unintended consequences. They are powerful, but they can bite. Here’s hoping they don’t bite you the same way.

Improving query performance

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Sometimes a database will start to run slowly, and you will need to trace the problem. There are many reasons for poor database performance, particularly over a network. They include:

  • Opening a form based on a large table or query, without filtering it first
  • Linking to multiple images in a network directory
  • Using a single copy of a database front end on a network drive, and opening your database via that networked front end
  • In short, anything that causes you to pull large amounts of data to your desktop.

If you haven’t made these design errors the time has come to look at your queries; you may have one or more queries that form the basis for a group of forms and reports, and if they are running slowly you can make a big difference to the database’s responsiveness by redesigning the queries.

Checking your queries

When this happened to me recently I built a function that opened all of the queries in the database, timing how long they took to run, and writing the results to the Immediate code window. I ran the function 4 times, copied the output to Excel, built a pivot table to average the results by query, and sorted the times in descending order. It quickly became apparent that one group of queries was slower than the rest, which gave me a couple of targets to concentrate on. This code requires a reference to the Microsoft DAO 3.6 Object Library (2003 or earlier) or the Microsoft Office x.0 Database Access Engine Object Library (x is 12 for office 2007, 14 for Office 2010).

Function TimeQueries()
    Dim qdf As DAO.QueryDef
    Dim StartTime As Single, _
        EndTime As Single

    For Each qdf In CurrentDb.QueryDefs
        DoCmd.SetWarnings False
        If InStr(1, qdf.Name, "~") = 0 Then
            StartTime = Timer
            DoCmd.OpenQuery qdf.Name
            EndTime = Timer
        End If
        Debug.Print qdf.Name & "; " & (EndTime - StartTime)
        DoCmd.SetWarnings True
    Next qdf
End Function

Optimisations

I use subqueries fairly extensively and discovered that two queries in particular had subqueries in the criteria. In both cases those subqueries contained groups and / or domain functions like Max and First.

First fix: write the subquery values out to a table

The first query returned all records from an import table that matched specific criteria, and took around 3 seconds to open. The import is a monthly process and takes a couple of minutes to complete, so I decided to make a table using the query data, as part of the process. When the ‘slow’ queries were based on this table instead of the base query, execution time dropped to 0.15 seconds: a 95% saving. This particular query was the main culprit; after the redesign, the database performance returned to its original speed before the slowdown.

Second fix: join to a second query

The slowest query fortunately doesn’t get used very often; it took around 150 seconds to run. Removing the criteria caused the query to open almost immediately so I turned the criteria into a second query, and joined it to the first on the primary key. Re-timing the query showed that it now opened in 0.15 seconds. This was a thousand-fold improvement over the starting query.

The bottom line

There are many ways to build queries but you may find yourself using one or two favourite techniques most of the time. If things slow down, you can get a significant performance boost by redesigning a couple of key queries.