>>Hi Naomi,
>>
>>IMHO, safety is varchar(10).
>>
>>MartinaJ
>>
>
>Hi Martina,
>
>Can you also explain why, say, varchar(10) is better than CHAR(10) for this particular case? If we always expect 10 digit number and we want to have this column to be a PK, would at least char(10) make better sense?
>
>We had our meeting in regards to this table and sort of decided to go with the char (or varchar(10))...
>
>Thanks.

Hmm,

Long experience from middle europe - if identificator has size 10 characters, then this rule is valid next five/three/one year ;-).
OK, NPI is very "stable" and CHAR(10) can be good choice. But VARCHAR(10) can be good choice for future.

MartinaJ