>>>

SELECT state FROM table2 ;
>>>  WHERE State NOT IN (SELECT state FROM table1)
>>>* or using correlated query
>>>SELECT state FROM table2 ;
>>>  WHERE NOT EXISTS (SELECT state FROM table1 WHERE state = table2.state )
>>>
>>>

>>
>>While VFP might optimize a correlated subquery like yours, in generally, when you can write a readable query without a correlated subquery, it's a better choice. (To the best of my knowledge, any correlated EXISTS query can be rewritten as an IN query, but sometimes the result is pretty obscure.)
>>
>
>I've to disagree with you here because wich query is faster depends on the query itself and data it is ran against. I don't know about any tests that shows that query without a correlated subquery is always faster. Also if you move to Sql Server you will find that correlated subquery is recomended over other approch because it's faster in most cases.

The point is that in most cases, for a correlated subquery, the subquery has to be executed once for each value referenced from the outer query. (In your example, that's table2.state.) I suspect that VFP recognizes and optimizes this case, so that there's no penalty, but I also suspect that in more complex cases, you may pay it.

I can't speak for SQL Server because I don't have experience with it.

Tamar