Managing and debugging SQL queries in MS Access

Question

MS Access has limited capabilities to manage raw SQL queries: the editor is quite bad, no syntax highlighting, it reformats your raw SQL into a long string and you can't insert comments.

Debugging complex SQL queries is a pain as well: either you have to split it into many smaller queries that become difficult to manage when your schema changes or you end-up with a giant query that is a nightmare to debug and update.

How do you manage your complex SQL queries in MS Access and how do you debug them?

Edit
At the moment, I'm mostly just using Notepad++ for some syntax colouring and SQL Pretty Printer for reformatting sensibly the raw SQL from Access.
Using an external repository is useful but keeping there's always the risk of getting the two versions out of sync and you still have to remove comments before trying the query in Access...

Answer 1

Are you talking here about what MS-Access calls 'queries' and SQL call 'views' or about the 'MS-Access pass-through' queries which are SQL queries? Someone could get easily lost! My solution is the following

1. free SQL Server Management Studio Express, where I will elaborate and test my queries
2. a query table on the client side, with one field for the query name (id_Query) and another one (queryText, memo type) for the query itself.

I then have a small function getSQLQuery in my VBA code to be used when I need to execute a query (either returning a recordset or not):

Dim myQuery as string, _
    rsADO as ADODB.recorset

rsADO = new ADODB.recordset
myQuery = getSQLQuery(myId_Query)

'if my query retunrs a recordset'
set rsADO = myADOConnection.Execute myQuery
'or, if no recordset is to be returned'
myADOConnection.Execute myQuery

For views, it is even possible to keep them on the server side and to refer to them from the client side

set rsADO = myADOConnection.execute "dbo.myViewName"

Answer 2

Debugging is more of a challenge. If a single column is off, that's usually pretty easy to fix. But I'm assuming you have more complex debugging tasks that you need to perform.

When flummoxed, I typically start debugging with the FROM clause. I trace back to all the tables and sub-queries that comprise the larger query, and make sure that the joins are properly defined.

Then I check my WHERE clause. I run lots of simple queries on the tables, and on the sub-queries that I've already checked or that I already trust, and make sure that when I run the larger query, I'm getting what I expect with the WHERE conditions in place. I double-check the JOIN conditions at the same time.

I double-check my column definitions to make sure I'm retrieving what I really want to see, especially if the formulas involved are complicated. If you have something complicated like a coordinated subquery in a column definition

Then I check to see if I'm grouping data properly, making sure that "DISTINCT"'s and "UNION"'s without UNION ALL don't remove necessary duplicates.

I don't think I've ever encountered a SQL query that couldn't be broken down this way. I'm not always as methodical as this, but it's a good way to start breaking down a real stumper.

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One thing I could recommend when you write your queries is this: Never use SELECT * in production code. Selecting all columns this way is a maintenance nightmare, and it leads to big problems when your underlying schemas change. You should always write out each and every column if you're writing SQL code that you'll be maintaining in the future. I saved myself a lot of time and worry just by getting rid of "SELECT *"'s in my projects.

The downside to this is that those extra columns won't appear automatically in queries that refer to "SELECT *" queries. But you should be aware of how your queries are related to each other, anyway, and if you need the extra columns, you can go back and add them.

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There is some hassle involved in maintaining a code repository, but if you have versioning software, the hassle is more than worth it. I've heard of ways of versioning SQL code written in Access databases, but unfortunately, I've never used them.

Answer 3

For debugging, I edit them in a separate text editor that lets me format them sensibly. When I find I need to make changes, I edit the version in the text editor, and paste it back to Access, never editing the version in Access.

Still a major PITA.