Queries are a great way to learn other aspects of database coding without really trying - just doing it by rote and understanding the process of queries can be an enlightening step to more advanced Access database creation.

For example, Queries are excellent for learning SQL (Structured Query Language) because it implements the same methods, but you do not need to know the ins and outs of the coding to be able to use it. Queries allow you to manipulate and understand tables and their relationships better. When looking at many records at once, queries can help you to see the "big picture" and update your view in real-time as to how your database is working.

When working with fields, Access and its queries give you more manipulation options. You can rename fields so that other people who use or edit your database can clearly see the meaning of them, whereas sometimes with other database software, you are stuck with generic terms that not everyone will recognise the meaning of. You can build expressions that work closely with your fields to better improve your database and your ability to share it.

Queries can get more and more advanced in tandem with the expertise of the user. You can customise functions and parameters, and create advanced queries. Amazingly, you can even base queries on OTHER queries in the same Access database, or have multiple stacks of tables working together. If you have the know-how, you can also couple queries with VBA functions (even user-defined ones) too.

Access has many wonderful query features, and when everything works fine, databases tick over, and the way forward is smooth. However, when working with queries and sub queries, there can be temperamental parts of the program that require a little understanding and troubleshooting to get past them. Queries are used frequently in Access, so learning to spot - and fix - the most frequently occurring ones can really ease your database woes.

For example, the unknown JET error is quite common. Perhaps you have joined up some tables incorrectly, or attaching a sub query as source for a query (or vice versa). This creates either a JET error or saying that Access's engine database has an error. Try to use the JOIN command rather than a sub query, but remember to test the database in real life when you're trying to de-bug after this error.

Another common mistake when using Access queries is when a query and a sub query use the same data - this usually will cause and error and your database not to work. When using the same table, it's best to alias your queries so you are not confusing the two types of query.

Even if you're not all that au fait with queries, there is still a Query Wizard built into Access that will let you start to understand and use the most common types of query. A little training in queries will go a long way towards you improving your Access experience, because so much of database programming depends on them. Master the query, and you will master your databases a lot better than before.