Gar,

Take a look at SQL Server 7.0's new English Query tool. It might give you some ideas.

In general, you can expect to have to provide some heuristics in the code to sort through what the user really wants. Logical AND and ORs aren't logical to them. In your example, Texas AND California makes perfect sense to an end user as it's natural language. Relationally, we know there will never be any hits on a direct translation of that. What is needed is a visual or verbal qualifier in natural language or a preparser:

Visual:

Sales in Texas
Sales in California

Sales in Texas AND California should not be allowed because it makes no sense to the relational model; the interface should not allow an AND where the column is the same. Or it can allow it and the pre-parse it before attempting to execute the query and change it to an OR.

>How would you design a query interface friendly enough for this customer?