您如何将googol存储在数据库中（以及其他非常大的数字）？

Question

How do you efficiently store very large and very small numbers from say 10^-100 to 10^100 , so that you can use them to calculate values in a programming language like JavaScript.

JavaScript stores 10^100 as 1e+101 , is there a way to do that in the database? The numbers would not often be that large, but I would like to do calculations with data such as 10^-34 * 2^16 or whatever, so the database should (I think) be storing these as numbers...

How does this work? How do you store numbers of this scale such that you can run computations with them?

By "the database", I'm thinking in general. I am messing around with MongoDB and Neo4j currently.

Answer 1

Databases themselves don't support numbers of arbitrary size in a native numeric format. Your general upper limit on numeric types is usually 8 bytes, which isn't anywhere near a googol.

You'll have to store the number either as a string (least efficient, easiest to work with, can be as precise as needed), as a byte array of arbitrary length (more efficient, harder to work with, still arbitrary precision), or in scientific notation (most efficient, harder to work with, and limited precision).

The first two, unfortunately, do eliminate the possibility of doing any server-side computation, since there wouldn't be a native numeric type that could support the range of valid values. All of the computation would have to be done client-side using a suitable numeric type.

Answer 2

If I were you, I'd separate the numerical value from the exponent. I personally don't have experience with MongoDB or Neo4j, but in MySQL (I'm sure they have similar terms) I'd create a table with an VARCHAR (text) column with whatever precision you'd like in your program (or how many unique numbers), and another VARCHAR column with length 3 (for max exponent 999). You can tinker with the values as you see fit, but that's all I can think of. If you want more flexible size values, I'd store the numbers on the server's file system using PHP rather than use databases.

Answer 3

You could use the double type.

The MySQL DOUBLE[(M,D)]

A normal-size (double-precision) floating-point number. Permissible values are -1.7976931348623157E+308 to -2.2250738585072014E-308, 0, and 2.2250738585072014E-308 to 1.7976931348623157E+308. These are the theoretical limits, based on the IEEE standard. The actual range might be slightly smaller depending on your hardware or operating system.