>>Ben,
>>
>>May I ask why you're using STR() to index and not another function?
>
>Hi George,
>
>In my former job we used compound index with STR function. Would it mean, that we will have performance hit in our queries? :(

I believe so, Nadya. As I said to Ben, unless the values are used in a calculation, it's better to go with character rather than numeric.