问题
Database newbie here. I'm setting up a mysql table. One of the fields will accept a value in increment of a 0.5. e.g. 0.5, 1.0, 1.5, 2.0, .... 200.5, etc.
I've tried int but it doesn't capture the decimals.
`value` int(10),
What would be the smallest type that can accommodate this value, considering it's only a single decimal.
I also was considering that because the decimal will always be 0.5 if at all, I could store it in a separate boolean field? So I would have 2 fields instead. Is this a stupid or somewhat over complicated idea? I don't know if it really saves me any memory, and it might get slower now that I'm accessing 2 fields instead of 1
`value` int(10),
`half` bool, //or something similar to boolean
What are your suggestions guys? Is the first option better, and what's the smallest data type in that case that would get me the 0.5?
回答1:
You'll want to look at the DECIMAL(P,S) type.
For that, P is the precision and S is the scale. You can think of P as how many digits there are in total (both before and after the decimal point), and S as how many of the digits are after the decimal point.
So for instance, to store from -999.99 to 999.99, you'd need 5 digits of precision and a scale of 2, therefore you'd use DECIMAL(5, 2).
In your case, you'd need a DECIMAL(n, 1), where n is how many digits you need before the decimal point + 1 for the decimal.
回答2:
You can use
DECIMAL(N,1)
Where N is the precision that represents the max number of significant digits that can be stored.
回答3:
Apart from using DECIMAL, you could store the tenfold of the value in an INT column (which I would think could be more efficient.)
- 0.5 => 5
- 201.5 => 2015
- etc.
来源：https://stackoverflow.com/questions/2708008/smallest-mysql-type-that-accommodates-single-decimal