Large Number or 10 Small Ones?

PantherX

Hey, I'm kinda new to MySQL... or at least doing it right.

So I was wondering, would it matter in a table if I were to have one long number like 10101010101010101010 and then do bit manipulation to get at each number I actually want in PHP

-or-

just have 10 fields with a 10 in each one?

Would either matter much when it comes to performance?

Thanks.

kevinsequeira

the large number is better in the sense that at a later stage what if u need to add another field, then u need to redesign the table,
also have the column as a varchar and each field value delimited by a comma or someother delimter

reg
kevin

PantherX

Thanks for the insight. That's actually not a bad idea.

I guess my main question is in db performance. Eventually I intend to have anywhere from 500 people using this db at the same time. So I'm more concerned about performance of the db.

BeastRider

a) What is 01010101010101010101010? You say "number" but that is fast and loose.

$a = 010101010101010101010101010 gets treated as an octal representation of a number (leading zero). If it is bigger than the max integer value, you get a float back, not an integer.

$b = 1010101010101010101010101010 gets treated as a decimal representation of a number (no leading zero). If it is bigger than the max integer value, you get a float back, not an integer.

$c = "010101010101010101010101010" gets treated as a string, and each character takes 8 bits... so you are not doing bit manipulation at all, you are manipulating substrings within a string.

b) Be careful of bit manipulation in php, particularly shifts. There is no unsigned integer in php, thus the results in php don't generally match the results in a compiled program language.

c) MySql permits the storage of unsigned integers but that really doesn't do you any good because you can't have an unsigned integer in php.

So, if you are talking true bit manipulation, you are talking 4 bytes of data for 32 bits, which is of type integer in both php and mysql.

PantherX

Originally posted by kevinsequeira
the large number is better in the sense that at a later stage what if u need to add another field, then u need to redesign the table,
also have the column as a varchar and each field value delimited by a comma or someother delimter

reg
kevin

Yes, this seems to be the way to go. Although, I'm now having problem with the DEFAULT part of things still.

How DOES one set a default with a string like this?

It is unfortunate that this is a widely undocumented part of MySQL, at least in the official MySQL manual.

It's time for the Cubs/Yankees game, so I'll be back later.

kevinsequeira

well have default value "NULL" and then u can seperate values like this

1|0|1|NULL|1|0|NULL

reg
kevin

PantherX

I don't want it to be null. I want it to have a specific default.

jweissig

Hello,

Having commas and other delimiters in database fields is not good database design. Can I ask why you want to have a large numeric value? I am sure there is a better solution.

Also can you please define "long number", how long is long? And if you could split the number how would you?

Possible creating a cross-reference table? Give me a little more detail and I will explain the best solution.

Thanks,
- Justin

PantherX

It's either have one long number or lots of smaller ones. Doesn't really matter which. Each 'set' represents something.

BeastRider

Originally posted by PantherX
How DOES one set a default with a string like this?

So I was wondering, would it matter in a table if I were to have one long number like 10101010101010101010 and then do bit manipulation to get at each number I actually want in PHP

Sidebar note:

It is NOT bit manipulation in any sense of the word if you are playing around with strings. You are manipulating at least whole bytes when you play with strings.

Bit manipulation takes a byte, a short int, or a long int, and applies the operators AND, OR XOR, and SHIFT to the bits to obtain new combinations. If you are not doing this you are not doing bit manipulation as you stated in your original post.

When disk space was extremely expensive, using bit level data made a lot of sense, and it is still useful for sets, etc. But a more practical question right now is: what are you trying to store and why?

PantherX

Ok people, could you pay attention to the thread here before posting? I'd appreciate it. You're arguing crap that has been gone over already.

At this point my question is in a VARCHAR how can I set the default to:

10,10,10,10,10,10,10,10,10,10

BeastRider

Originally posted by PantherX
Ok people, could you pay attention to the thread here before posting? I'd appreciate it. You're arguing crap that has been gone over already.

At this point my question is in a VARCHAR how can I set the default to:

10,10,10,10,10,10,10,10,10,10

Tell ya what Panther... if you had made your original post in plain English instead of the gibberish about "numbers" and "bit manipulation", you might get meaningful responses.

And since you see fit to upbraid those that are trying to help you solve your problem, even if I (we) are on the wrong track, I have a suggestion for you: YOU FIGURE IT OUT.

Pay attention? I'm through wasting time!

PS: Dumb is just plain dumb.

PantherX

Hrm... I DID figure it out.

I'm sure you're quite upset about that, since now you can't prove how much smarter you are than me. :rolleyes:

Anyway, to the rest of you I'm sorry I wasted your time. Thank you for the opportunity to get an answer. 😃

BeastRider

Eh?