Thread: VARCHAR Field Length

As I understand it, a VARCHAR field type only uses the amount of space it needs for the data it contains, so does it have a huge affect on space useage if I make all my VARCHAR fields 255 in size, as opposed to making them different in length.

For example a LastName field may only need to be a size of 30, but would it make a difference to data storage if I made it 255 in size? If someone's surname was Smith, as I understand it, a field of 30 would use the same amount of space to store that name as a field of 255 would.

Personally i always use the maximum characters i expect/allow for a field.
So if the field should have max 10 characters, i set 10 for it.

Regarding your question, see if this link answers you!
What are the optimum varchar sizes for MySQL? - Stack Overflow

That helps alot m. Thanks.

Originally Posted by richyrich

That helps alot m. Thanks.

cool

Second micky here -- I always make my varchar field match the real world equivilents, thus if the max number of characters allowed in a name fied is 30, then I'll use 30.

You are correct in that varchar fields only use space as needed, tho the minimum length if I remember correctly is 2-bytes; basically the overhead for storing the length. Thus, varchars don't make much sense for storing short strings unless you expect a large number of empty values. For example, if I have a SKU that's 6 characters in almost every case, I'll use char(6) over varchar(6) in this case to save the 2-byte overhead. In other words, varchar makes the best sense when the length of the stored values is greatly variable or there are a large number of empty values.

Yeah. If I have a fixed length string, I'd use a CHAR field also.

I'm working on something where I'm not too sure what the maximum length will be (lots of chemical names and things! ) hence why I'm not sure what size to make some of the fields.

In that case, go with VARCHAR(MAX) or VARCHAR(8000) or whatever MySql supports and have no worries.