When I insert a number as 1234567.1234567 it will translate it to 1234567.1250.
How do I make it to save the correct number?
When I insert a number as 1234567.1234567 it will translate it to 1234567.1250
FLOATs are saved in four bytes, allowing for about 232 different values.
1234567.1234567 is not one of them. Encodable values are all some limited integer times a power of 2.
The closest encodable value is 1234567.125 or 9876537*2-3.
Code could use DOUBLE yet a similar issue applies.
The closest is about 1234567.1234567000065..., may be close enough for OP's purpose.
Related
In my database some fields (amount, balance) are assigned as floating value, but now i have a problem with that .if the amount is 1.56 it will take 1.6
then i alter the table using Round(amount,2)
still it shows the same problem.
if anybody know please help me.
The float fields must be declared as float(some_integer, 1) to show the behaviour you described. The first integer in such a declaration tells MySQL how much digits should be visible alltogether, the ones left to the decimal point + the ones right to it. To have 3 digits to the left and 2 to the right of the decimal point you would declare it as float(5,2).
Like Doan Cuong already mentioned it would be better if you would choose decimal data type.
See the different behaviour of it live here.
To quote the manual:
The DECIMAL and NUMERIC types store exact numeric data values. These types are used when it is important to preserve exact precision, for example with monetary data.
The FLOAT and DOUBLE types represent approximate numeric data values.
For additional info about the data types read more here.
In general, I have double values that I work with. I use them as double values and also as strings (in application code). I store them as Double in my MySQL database.
The problem I have is with trailing 0's. For example, the value I get is 10.60. This value gets truncated down to 10.6 which is not ok for me. I need that trailing 0.
I also need it to not add 0's. For example, if I got 10.60, it should not add 0's to be 10.600. I am not sure which data type fits my needs. It needs to be stored as the double value, but keep its trailing 0's, and not add any additional 0's.
Can anyone assist me in which data type to use?
I would store the double values in a double/real field only and not varchar so as to not lose any precision during conversion. Since the issue is only in application code, I would round them to the appropriate decimal places (using the ROUND() function) while retrieving from the database.
I understand what a datatype is (intuitively). But I need the formal definition. I don't understand if it is a set or it's the names 'int' 'float' etc. The formal definition found on wikipedia is confusing.
In computer programming, a data type is a classification identifying one of various types of data, such as floating-point, integer, or Boolean, that determines the possible values for that type; the operations that can be done on values of that type; the meaning of the data; and the way values of that type can be stored.
Can anyone help me with that?
Yep. What that's saying is that a data type has three pieces:
The various possible values. So, for example, an eight bit signed integer might have -127..128. This of that as a set of values V.
The operations: so an 8-bit signed integer might have +, -, * (multiply), and / (divide). The full definition would define those as functions from V into V, or possible as a function from V into float for division.
The way it's stored -- I sort of gave it away when I said "eight bit signed integer". The other detail is that I'm assuming a specific representation by the way I showed the range of values.
You might, if you're into object oriented programming, notice that this is very much like the definition of a class, which is defined by the storage used by each object, adn the methods of the class. Providing those parts for some arbitrary thing, but not inheritance rules, gives you what's called an abstract data type.
Update
#Appy, there's some room for differences in the formalities. I was a little subtle because it was late and I was suddenly uncertain if I'd assumed one's complement or two's complement -- of course it's two's complement. So interpretation is included in my description. Abstractly, though, you'd say it is a algebraic structure T=(V,O) where V is a set of values, O a set of functions from V into some arbitrary type -- remember '==' for example will be a function eq:V × V → {0,1} so you can't expect every operation to be into V.
I can define it as a classification of a particular type of information. It is easy for humans to distinguish between different types of data. We can usually tell at a glance whether a number is a percentage, a time, or an amount of money. We do this through special symbols %, :, and $.
Basically it's the concept that I am sure you grock. For computers however a data type is defined and has various associated attributes, like size, like a definition keywork (sometimes), the values it can take (numbers or characters for example) and operations that can be done on it like add subtract for numbers and append on string or compare on a character, etc. These differ from language to language and even from environment to env. (16 - 32 bit ints/ 32 - 64 envs./ etc).
If there is anything I am missing or needs refining please ask as this is fairly open ended.
The round function sometime doesn't work very well. I have in my db a row like this:
field_1= 375
field_2= 0.65
field_3= 0.1
field_4= 11
So we know that: field_1*field_2*field_3*field_4 = 268.125 so if I round it to 2 decimals -> 268.13.
But in mysql I got 268.12 -> Select round(field_1*field_2*field_3*field_4) from my table -> 268.12
This situation just happens with these values, I tried with other numbers and no problem the round works.
Any workaround about it. I tried in mysql 4.1.22, and 5.1.44 and I get the same issue. I read in other forum http://bugs.mysql.com/bug.php?id=6251 that it is not a bug, they said that it depends on the C library implementation.
What data type are you using for those columns?
If you want exact precision then you should use NUMERIC or DECIMAL, not FLOAT, REAL, or DOUBLE.
From the manual:
The DECIMAL and NUMERIC types store exact numeric data values.
These types are used when it is important to preserve exact precision,
for example with monetary data.
If applicable you can use FLOOR()
If not applicable you will be better off handling this on the application side. I.e. do the entire calculation application side and then round, or just round application side.
SELECT (field_1*field_2*field_3*field_4) AS myCalculation FROM my table
in xxxx.mxml (from flex) i have called the remote remote method (of java) the method return type is float
in the xxxx.mxml's remote objects result handler i need get the float values as Numeric.....or String..i tried with string...i did Alert.show to see the value some times i get exact value for eg, 0.5 is the value returning from java methid but here it will show 0.50000454...so on..how get the exact value?
It is because of the way floating point numbers are stored; basically they can't be stored precisely. A quick search in SO would reveal a lot of threads about this. Also read "What Every Computer Scientist Should Know About Floating-Point Arithmetic"
Thus the problem of getting the exact value boils down to what you define exact to be. Try rounding it to a given number of floating points at java end, convert the rounded number to a string (I'm not sure if this conversion would preserve the precision) and send that string.