varchar versus char

[timscronin]

I no this is like arguing politics, but isn't there a formula for using varchar versus char? I realize there is some overhead with varchar, but if a majority of our data fields are empty(not my desing and cna't change), wouldn't the varchar be better

 

[SQLBill]

I would use VARCHAR. Somewhere I saw just exactly how much room would be used by a NULL value in CHAR and VARCHAR. I believe the CHAR uses 1 byte (default for CHAR is CHAR(1)). With VARCHAR a NULL does't have any length so it's equivlent to VARCHAR(0). Again, that's the way I remember seeing it explained.

-SQLBill