I have the tables, Widgets and Categories, and a table WidgetCategories that expresses the many-to-many relationship...
between a Widget and a Category. Each widget has a 'price' field. I want to write a query that, given a category id, returns the most expensive widget of that category. I end up wanting to do something like (pardon the pseudo-SQL):
tempTable := SELECT widgetID, price FROM Widgets, WidgetCategories WHERE Widgets.widgetID = WidgetCategories.widgetID AND WidgetCategories.categoryID = $given_category$
where $given_category$ is the category I'm interested in, followed by
SELECT widgetID, price FROM tempTable WHERE price = MAX(price)
My solution seems very awkward, with the creation of a temp table. Is there any way to do this better?
You're almost there. Just make your temp table query a subquery of the retrieval query:
select Widgets.widgetID , price from Widgets , WidgetCategories where Widgets.widgetID = WidgetCategories.widgetID and WidgetCategories.categoryID = $given_category$ and price = ( select max(price) from Widgets , WidgetCategories where Widgets.widgetID = WidgetCategories.widgetID and WidgetCategories.categoryID = $given_category$ )
Note that both the outer query and subquery need to check for the selected category.
For More Information
- Dozens more answers to tough SQL questions from Rudy Limeback.
- The Best SQL Web Links: tips, tutorials, scripts, and more.
- Have an SQL tip to offer your fellow DBAs and developers? The best tips submitted will receive a cool prize. Submit your tip today!
- Ask your technical SQL questions -- or help out your peers by answering them -- in our live discussion forums.
- Ask the Experts yourself: Our SQL, database design, Oracle, SQL Server, DB2, metadata, object-oriented and data warehousing gurus are waiting to answer your toughest questions.
Dig Deeper on Oracle and SQL
Have a question for an expert?
Please add a title for your question
Get answers from a TechTarget expert on whatever's puzzling you.