I have reviewed the previous Questions and haven't found the answer to the following question,
Is there a Database Tool available in MS Access to run and identify the Queries that are NOT Bring used as a part of my database. We have lots of Queries that are no longer used and I need to clean the database and get rid of these Queries.
Access does have a built in “dependency” feature. The result is a VERY nice tree-view of those dependencies, and you can even launch such objects using that treeview of your application to “navigate” the application so to speak.
The option is found under database tools and is appropriately called Object Dependencies.
The result looks like this:
While you don't want to use auto correct, this feature will force on track changes. If this is a large application, then on first run a significant delay will occur. After that, the results can be viewed instantly. So, most developers still turn off track name autocorrect (often referred to track auto destroy). However, the track auto correct is required for this feature.
And, unfortunately, you have to go query by query, but at least it will display dependences for each query - (forms, or reports). However, VBA code that creates SQL on the fly and uses such queries? Well, it will not catch that case. So, at the end of the day, deleting a query may well still be used in code, and if that code creates SQL on the fly (as at LOT of VBA code does, then you can never really be sure that the query is not not used some place in the application.
So, the dependency checker can easy determine if another query, another form/sub form, or report uses that query. So dependency checker does a rather nice job.
However, VBA code is a different matter, and how VBA code runs and does things cannot be determined until such time code is actually run. In effect, a dependency checker would have to actually run the VBA code, and even then, sometimes code will make several choices as to which query to run, or use - and that is determined by code. I suppose that you could do a quick "search", since a search is global for VBA (all code in modules, reports and forms can be searched). This would find most uses of the query, but not in all cases since as noted VBA code often can and does create sql on the fly.
I have a vague recollection part of Access Analyzer from FMS Inc has this functionality built in.
Failing that, I can see 2 options that may work.
Firstly, you could use the inbuilt Database Documenter. This creates a report that you can export to Excel. You would then need to import this into the database, and write some code that loops the queries to see if they appear in this table;
Alternatively, you could use the undocumented "SaveAsText" feature to loop all Forms/Reports/Macros/Modules in your database, as well as looping the Querydefs and saving their SQL into a text file. You would then write some VBA to loop the queries, open each of the text files and check for the existence of the query.
Either way, rather than just deleting any unused queries, rename then to something like "old_Query", and leave them for a month or so in the database just in case!!
Regards,
I'm creating an application for work in which I need to be able to disable the app if I leave the company. I'll maintain ownership and this agreement to cancel upon my departure is agreed upon in our contract.
Since these apps will be used by other people, I need to perform a "check" upon launching as to whether access is still granted or not.
I know that MySQL would be perfect for this by simply storing a 0 or 1 in a TINYINT table, but I don't want to use MySQL for this small task since I'd have to use free hosting which has proven hard in finding reliable hosts with remote access enabled.
Ideally I'd like a website that offers a personalized URL like http://randomURL.com/X38DAKNLD828ND that I could store a simple piece of text like "Enabled" or "Disabled".
There must be some simple way to store such a small piece of data?
Just try parse.com
If you're writing a small/simple app (or a throwaway prototype) with little to no logic on the backend then go for it, but for something larger/scalable it's best to avoid it, I can say that from first hand experience
I am trying to build a user interface which will allow users to choose what kind of information they want, then based on these selected conditions, I need to query an access database and retrieve the corresponding data for future calculation. During calculation, there are two additional tables that I will query from. Finally, I need to display the calculated results to users. Now I have some questions:
Which one will be easier if I use excel as a front-end to users and retrieve querying data from Access to excel vs. I use access forms as a front-end to users and directly work with access to query data?
Does access forms can perform functions like allow users to select options from a drop down list? and once options selected, Access will query the target info?
Can Access perform intermediate calculation for large amount records? Will it get very slow? Compared to excel, which one is better in terms of calculation?
I never use Access before and just know a little about Excel VBA, not totally familiar with it, not to mention object models. So, in this case, which way is time-saving for me? or they are probably the same time-consuming?
Anything else that I should be aware of?
Thanks so much!
Bing
Definitely Access - it is specifically made for working with, querying, and reporting on data. The language of VBA that you have experience with in Excel is the exact same language used for coding in MS Access!
Access, no question!
Absolutely. Of course it doesn't magically know this as your requirement. You have to drop the combo box on the form yourself, and then in the OnChange event of the combo box, alter a query statement that displays results to filter based on the user's selection.
Sure. Make a temp table (a table that is only used for the calculation), populate the records with INSERT statements, apply intermediate calculations with UPDATE statements, and display the results. Access is built for this kind of thing and will most likely be faster than Excel.
Access uses VBA as well. There may be a larger learning curve to switch, but if you are familiar with the user interface objects in Excel such as Button, Combo Box, etc., they will be very similar and yet more intuitive in Access (Because that's what Access was made for)
Access has some quirks. Google a few tutorials and get some background on the ways Access is traditionally used for your kinds of scenarios and it will go a long way toward streamlining your development.
Start with the simplest model that will accomplish what your requirements are, and implement it. Then work through the quirks and bugs that you find with Google as your friend, and you should be able to get something solid pretty quickly! As you get into the experience, feel free to post new questions with specific problems you find along the way.
Best Regards,
A while back I asked this question about splitting an MS Access application, and possibly leaving some of the non-table functionality in the BE. Well, I'm at it again... :)
Some of my tables will be such that they are never updated by the user. The data feed to these tables will be a fairly intensive code process, run daily, that extracts from Oracle, majorly massages the data & then writes to my tables (very different structure from Oracle).. There's no practical way to make it a live link to Oracle. All of the code for this will be in Modules/Class Modules, none in Forms. It absolutely would need to be changed if the schema of either the Access file or the Oracle server changes.
Given the foregoing, FE or BE?
I would put the code modules in a FE so that you can re-link a copy of the FE to a testing/development BE as the need arises. The code FE needn't be the same application FE you distribute to your users.
I don't know that I'm understanding your description -- from what I get it sounds like a temp table, i.e., with data that is replaced with something else on a regular basis. In that case, you certainly don't want it either in your front end or in your back end (if the back end is a Jet/ACE database). If that's what you have here, this data belongs in a separate back end.
For managing links to multiple back ends, you might find my Reconnect Utility useful. Since all of my apps have a temp database that's part of the front end, all of them need the ability to easy reconnect to more than one back end (the linked table manager is a real pain for that). Some of my apps have as many as four different target databases that the linked tables point at, and it's much easier to do that with my utility. It only works with Jet/ACE back ends, though (I've sketched out handling of other data sources, but never finished it, because I never needed it in any of my own applications!).
I have created an MS Access 2003 application, set up as a split front-end/back-end configuration, with a user group of about five people. The front end .mdb sits on a network file server, and it contains all the queries, forms, reports, and VBA code, plus links to all the tables in the back end .mdb and some links to ODBC data sources like an AS/400. The back end sits on the same network file server, and it just has the table data in it.
This was working well until I "went live" and my handful of users started coming up with enhancement requests, bug reports, etc. I have been rolling out new code by developing/testing in my own copy of the front-end .mdb in another network folder (which is linked to the same back-end .mdb), then posting my completed file in a "come-and-get-it" folder, alerting the users, and they go copy/paste the new front-end file to their own folders on the network. This way, each user can update their front end when they're at a 'stopping point' without having to boot everyone out at once.
I've found that when I'm developing now, sometimes Access becomes extremely slow. Like, when I am developing a form and attempt to click a drop-down on the properties box, the drop-down arrow will push in, but it will take a few seconds before the list of options appears. Or there's tons of lag in selecting & moving controls on a form. Or lots of keyboard lag.
Then, at other times, there's no lag at all.
I'm wondering if it's because I'm linked to the same back end as the other users. I did make a reasonable effort to set up the queries, forms, reports etc. with minimal record locking, if any at all, depending on the need. But I may have missed something, or perhaps there is some other performance issue I need to address.
But I'm wondering if there is an even better way for me to set up my own development back-end .mdb, so I can be testing my code on "safe" data instead of the same live data as the rest of the users. I'm afraid that it's only a matter of time before I corrupt some data, probably at the worst possible moment.
Obviously, I could just set up a separate back-end .mdb and manually reconfigure the table links in the front end every time, using the Linked Table Manager. But I'm hoping there is a more elegant solution than that.
And I'm wondering if there are any other performance issues I should be considering in this multi-user, split database configuration.
EDIT: I should have added that I'm stuck with MS Access (not MS-SQL or any other "real" back end); for more details see my comment to this post.
If all your users are sharing the front end, that's THE WRONG CONFIGURATION.
Each user should have an individual copy of the front end. Sharing a front end is guaranteed to lead to frequent corruption of the shared front end, as well as odd corruptions of forms and modules in the front end.
It's not clear to me how you could be developing in the same copy of the front end that the end users are using, since starting with A2000, that is prohibited (because of the "monolithic save model," where the entire VBA project is stored in a single BLOB field in a single record in one of the system tables).
I really don't think the problems are caused by using the production data (though it's likely not a good idea to develop against production data, as others have said). I think they are caused by poor coding practices and lack of maintainance of your front end code.
turn off COMPILE ON DEMAND in the VBE options.
make sure you require OPTION EXPLICIT.
compile your code frequently, after every few lines of code -- to make this easy, add the COMPILE button to your VBE toolbar (while I'm at it, I also add the CALL STACK button).
periodically make a backup of your front end and decompile and recompile the code. This is accomplished by launching Access with the /decompile switch, opening your front end, closing Access, opening your front end with Access (with the SHIFT key held down to bypass the startup code), then compacting the decompiled front end (with the SHIFT key held down), then compiling the whole project and compacting one last time. You should do this before any major code release.
A few other thoughts:
you don't say if it's a Windows server. Linux servers accessed over SAMBA have exhibited problems in the past (though some people swear by them and say they're vastly faster than Windows servers), and historically Novell servers have needed to have settings tweaked to enable Jet files to be reliably edited. There are also some settings (like OPLOCKS) that can be adjusted on a Windows server to make things work better.
store your Jet MDBs in shares with short paths. \Server\Data\MyProject\MyReallyLongFolderName\Access\Databases\ is going to be much slower reading data than \Server\Databases. This really makes a huge difference.
linked tables store metadata that can become outdated. There are two easy steps and one drastic one to be taken to fix it. First, compact the back end, and then compact the front end. That's the easy one. If that doesn't help, completely delete the links and recreate them from scratch.
you might also consider distributing an MDE to your end users instead of an MDB, as it cannot uncompile (which an MDB can).
see Tony Toews's Performance FAQ for other generalized performance information.
1) Relink Access tables from code
http://www.mvps.org/access/tables/tbl0009.htm
Once I'm ready to publish a new MDE to the users I relink the tables, make the MDE and copy the MDE to the server.
2) I specifically created the free Auto FE Updater utility so that I could make changes to the FE MDE as often as I wanted and be quite confident that the next time someone went to run the app that it would pull in the latest version. For more info on the errors or the Auto FE Updater utility see the free Auto FE Updater utility at http://www.granite.ab.ca/access/autofe.htm at my website to keep the FE on each PC up to date.
3) Now when working on site at a clients I make the updates to the table structure after hours when everyone is out of the system. See HOW TO: Detect User Idle Time or Inactivity in Access 2000 (Q210297) http://support.microsoft.com/?kbid=210297 ACC: How to Detect User Idle Time or Inactivity (Q128814) http://support.microsoft.com/?kbid=128814
However we found that the code which runs on the timer event must be disabled for the programmers. Otherwise weird things start happening when you're editing code.
Also print preview would sometimes not allow the users to run a menu item to export the report to Excel or others. So you had to right click on the Previewed report to get some type of internal focus back on the report so they could then export it. This was also helped by extending the timer to five minutes.
The downside to extending the timer to five minutes was if a person stays in the same form and at the same control for considerable parts of the day, ie someone doing the same inquiries, the routine didn't realize that they had actually done something. I'll be putting in some logic sometime to reset this timer whenever they do something in the program.
4) In reference to another person commenting about scripts and such to update the schema see Compare'Em http://home.gci.net/~mike-noel/CompareEM-LITE/CompareEM.htm. While it has its quirks it does create the VBA code to update tables, fields, indexes and relationships.
Use VBA to unlink and re-link your tables to the new target when switching from dev to prod. It's been to many years for me to remember the syntax--I just know the function was simple to write.
Or use MS-Access to talk to MS-Access through ODBC, or some other data connection that lives outside of the client mdb.
As with all file base databases, you will eventually run into problems with peak usage or when you go over a small magical number somewhere between 2 and 30.
Also, Access tends to corrupt frequently, so backup, compact and repair need to be done on an frequent basis. 3rd party tools used to exist to automate this task.
As far as performance goes, the data is being processed client side, so you might want to use something like netmeter to watch how much data is going over the wire. The same principle about indexing and avoiding table scans apply to file base dbs as well.
Many good suggestions from other people. Here's my 2 millicents worth. My backend data is on server accessed through a Drive mapping. In my case, the Y drive. Production users get the mapping through a login script using active directory. Then the following scenarios are easily done by batch file:
Develop against local computer by doing a subst command in a batch file
run reports against last nights data by pointing Y to the backup server (read only)
run reports against end of month data by pointing to the right directory
test against specialized scenarios by keeping a special directory
In my environment (average 5 simultaneous users, 1000's of rows, not 10,000's.) corruption has occurred, but it's rare and manageable. Only once in the last several years have we resorted to the previous days backup. We use SQL Server for our higher volume stuff, but it's not as convenient to develop against, probably because we don't have a SQL admin on site.
You might also find some of the answers to this question (how to extract schemas from access) to be useful as well. Once you've extracted a schema using one of the techniques that were suggested you gain a whole range of new options like the ability to use source control on the schemas, as well as being able to easily build "clean" testing environments.
Edit to respond to comment:
There's no easy way to source control an Access database in it's native format, but schema files are just text files like any other. Hence, you can check them in and out of the source control software of your choice for easy version control/rollbacks.
Or course, it relies on you having a series of scripts set up to re-build your database from the schema. Once you do, it's normally fairly trivial to create an option/alternative version that rebuilds it in a different location, allowing you to build test environments from any previous committed version of the schema. I hope that clarifies a bit!
If you want to update the back end MDB schema automatically when you release a new FE to the clients then see Compare'Em http://home.gci.net/~mike-noel/CompareEM-LITE/CompareEM.htm will happily generate the VBA code need to recreate an MDB. Or the code to create the differences between two MDBs so you can do a version upgrade of the already existing BE MDB. It's a bit quirky but works.
I use it all the time.
You need to understand that a shared mdb file for the data is not a robust solution. Microsoft would suggest that SQL Server or some other server based database would be a far better solution and would allow you to use the same access front end. The migration wizard would help you make the changeover if you wanted to go that way.
As another uses pointed out, corruption will occur. It is simply a question of how often, not if.
To understand the performance issues you need to understand that to the server the mdb file with the data in it is simply that, a file. Since no code runs on the server, the server does not understand transactions, record locking etc. It simply knows that there is a file that a bunch of people are trying to read and write simultaniously.
With a database system such as SQL Server, Oracle, DB2. MySQL etc. the database program runs on the server and looks to the server like a single program accessing the database file. It is the database program (running on the server) that handles record locking, transactions, concurrency, logging, data backup/recovery and all the other nice things one wants from a database.
Since a database program designed to run on the server is designed to do that and only that, it can do it far better and more efficently that a program like Access reading an writing a shared file (mdb).
There are two rules for developing against live data
The first rule is . . . never develop
against live data. Not ever.
The second rule is . . .never develop
against live data. Not ever.
You can programatically change the bindings for linked tables, so you can write a macro to change your links when you're deploying a new version.
The application is slow because it's MS Access, and it doesn't like many concurrent users (where many is any number > 1).