I cannot insert the value "-1" into database, the table set the field is int(10).
I don't know what the problem is. Could you help me. thank you.
$sql2="INSERT INTO attendance_count(username,date,count_time,appendix)VALUES('$applicant','$date1','-1','$altext')";
mysql_query($sql2);
don't put single quote since its an int.
Make sure the column isn't UNSIGNED
the documentation is saying it won't store a literal "-" character,
which means it's probably now doing what the other signed INTEGER
fields have always done and it's storing a sign bit to denote negative
numbers instead.
You're still seeing a minus sign preceding the number because it's
being generated by MySQL as a result of that sign bit.
If you don't understand the sign bit, you can consider how a signed
byte can store numbers from -128 to 127, while an unsigned byte can
store numbers from 0 to 255. That's because one of the 8 bits in a
signed number is being used to store +/- (1 is negative, 0 is
positive), while the remaining bits offer numbers up to 2^7 (-128 or
127).
So, for example, if the bits 1111 had a sign bit they would equal -7
(negative+4+2+1), but if they were unsigned they'd equal 15 (8+4+2+1).
It's still the same amount of bits being stored.
You may wonder why the negative bound in a signed number can use the
8th bit, while the positive bound is limited to the sum of the 7 bits
(1 less than the 8th bit). This is because 10000000 is considered to
be both negative and the 8th bit simultaneously, because its
representation of -0 otherwise is redundant with 00000000 which
represents 0. There's no distinction between negative and positive
zero, so a negative most significant bit is always the value of that
bit itself (but negative).
the column where youre entering the value -1 should be SIGNED
INT(SIGNED) values can be a minimum of-2147483648 to a maximum of 2147483647
INT(UNSIGNED) values can be a minimum of 0 to a maximum of 4294967295
Related
I have been working on a project with a lot of numbers inserted in a database table. Now that I finished the code, I was checking the values for errors and I noticed my value 3075277 would transform in 3075280 when inserted in the db and 3075255 would be 3075260.
The colummn type is Float. What should I change to disable the rounding? This one doesn't even have decimals numbers, why would it round like that? I use the default options, only changed collation to utf8_general_ci and change the type to varchar and lenght in some and float in others.
This issue is with MySQL, not Phpmyadmin.
FLOAT has 6-7 significant digits of precision, as you are seeing with the mangled values. By "significant digits", I mean starting anywhere:
1234567xxxx.
12345.67xxx
1.234567xxx
0.0000001234567xxx
That is the xxx is likely to be zeros or some kind of 'noise', not the original value you put into the column.
DOUBLE gives you about 16 significant digits.
DECIMAL(9,0) gives you 9 digits to the left of the decimal point, none afterwards. Sort of like INT.
DECIMAL(9,4) gives you 5 (9-4) digits to the left of the point; 4 afterwards.
What kinds of numbers are you storing? Money? Scientific measurements? Astronomical distances? DT's wealth?
Now you are using FLOAT type but getting error because you are saving big decimal number in the database. You should go for DOUBLE.
Although FLOAT and DOUBLE are similar because they store the value in approximate value, but that DOUBLE is 8-bytes, and FLOAT is 4-bytes.
A FLOAT is for single-precision, while a DOUBLE is for double-precision numbers.
MySQL uses four bytes for single-precision values and eight bytes for double-precision values.
There is a big difference from floating point numbers and decimal (numeric) numbers, which you can use with the DECIMAL data type. This is used to store exact numeric data values, unlike floating point numbers, where it is important to preserve exact precision, for example with monetary data.
So as in your case, for larger numbers you would want DOUBLE instead of FLOAT.
The operation 1539 | 0xfffff800 returns -509 in JavaScript and Python 2.7.
In PHP I get 4294966787.
Does anybody know why and could explain that to me. I would love to know how I get the expected result in PHP as well.
1539 | 0xfffff800 = 4294966787 (= 0xFFFFFE03)
This is perfectly right. So, PHP is right.
If you would like to have both positive and negative integers, you need some mechanism to determine whether the number is negative. This is usually done using the 2-complement of the number. You can negate a number by just inverting all the bits of the number and then add 1 to it. In order to avoid ambiguities, you cannot use all the bits of your integer variable. You cannot use the highest bit in this case. The highest bit is reserved as a sign bit. (If you would not do so, you never know if your number is a big positive number or a negative number.)
For exammple with an 8 bit integer variable, you would be able to represent numbers from 0 to 255. If you need signed values, you can represent number from -128 (1000 000 binary) to +127 (0111 1111).
In your example, you have a 32 bit number which has its highest bit set. In Python and JavaScript, it's interpreted as negative number, as they apparently have 32 bit variables, and there, the highest bit is set. They interpret that as negative number. So, the result of your calculation is also negative.
In the PHP version you are using, the integer variable seems to be 64 bit long and only the lower 32 bits are used. The highest bit (bit 63) is not set, so PHP interprets this number as positive. Depending on what you want to achive, you may want to fill up all bits from bit 32 to bit 63 with 1s which will create a negative number...
I'm using a decimal data type in mysql. I set it to 6,2 but it won't allow 12105. It defaults to 10000 any time a number is inputted higher than 10000. How can I allow numbers like 12105 up to 5000000 and more.
This is a dup but I can't find it. DECIMAL(x,y) means the total number of digits (left OR right of the point) is x.
So, if you want to store between 0 and 999999.99, you need to define it as DECIMAL(8,2)
I have field where i store my grand total to a mysql filed as total and its type set as decimal(10,2)
When my php form adds up and updates the query for 112381348.40 (i.e 112 million)
but when i fetch or view it on phpMyadmin, the value shows as 99999999.99
from my data type set, it has to be 10 digits and 2 decimals where as it is maximum updating as 8 and 2.
Am i understanding wrong or what am i doing wrong.
I know i can increase it to decimal(13,2) and then see it.
But i would like to know the reason, why 10,2 is not happening?
The specification for decimal(m, n) takes two arguments. The first is the "precision" and the second is the "scale". More colloquially, the first is the number of digits in the number. The second is the number of digits to the right of the decimal point.
So, your specification of decimal(10, 2) can store numbers like: 12,345,678.90 -- i.e., up to 99,999,999.99. And that is the maximum number.
If you want to store numbers larger than that, then use a larger precision for the number. For your number, you need at least decimal(11, 2), although I would suggest a larger precision so you don't encounter this problem in the future.
In setting a float or decimal field, the first int value is the total character count. The second is how many decimal places. So:
//decimal(10,2)
12345678.90
//decimal(13,2)
12345678901.23
//decimal(7,3)
1234.567
See?
You have 11 digits. The first number is the total digits. Try:
DECIMAL(11, 2)
Lets assume we are talking about 32bit system.
PHP doesn't support unsigned INT. It means that INT value should be between -2,147,483,648 and 2,147,483,647 values. And INT takes 4 bytes to store a value which are 32 bits length.
So does it mean that I have only 31 bits for value and 1 bit for sign? Or I can use whole 32 bits to store a value?
You are using the whole 32 bits. It's just that the default output functions interpret it as signed integer. If you want to display the value "raw" use:
printf("%u", -1); // %u for unsigned
Since PHP handles the integers signed internally however, you can only use bit arithmetics, but not addition/multiplication etc. with them - if you expect them to behave like unsigned ints.
2147483647 is the usual value 2^31-1. 1 bit for sign and -1 because we also represent 0.
from the manual:
"The size of an integer is platform-dependent, although a maximum value of about two billion is the usual value (that's 32 bits signed). 64-bit platforms usually have a maximum value of about 9E18. PHP does not support unsigned integers. Integer size can be determined using the constant PHP_INT_SIZE, and maximum value using the constant PHP_INT_MAX since PHP 4.4.0 and PHP 5.0.5."
As far as i know on a 32-bit system the largest positive integer possible is 2147483647 values above will be float values, since a float value in php can take values up to 10000000000000.
First of all, if you want to do calculations with huge numbers (say, regulary greater than 10k), you should use the bcmath arbitrary precision module.
Secondly, the official php implementation uses the Two's complement internally to represent numbers, like virtually all other compilers and interpreters. Since the entropy of the signed bit (if you count 0 as positive[1]) is 1, and the entropy of 31 bits is, well, 31, you can store 232 = 4 294 967 296 distinct values. How you interpret them is up to your application.
[1] - 0 is neither positive nor negative.
Normally with 32 bit integers the difference between signed and unsigned is just how you interpret the value. For example, (-1)+1 would be 1 for both signed and unsigned, for signed it's obvious and for unsigned it's of course only true if you just chop the overflow off. So you do have 32 bits to store values, it just happens to be so that there's 1 bit that is interpreted differently from the rest.
Two's complement is most frequently used to store numbers, which means that 1 bit is not wasted just for the sign.
http://en.wikipedia.org/wiki/Two's_complement
In PHP if a number overflows the INT_MAX for a platform, it converts it to a floating point value.
Yes if it would have used unsigned integer it will use 32 bit to store it as you don't need sign in that case but as it supports only signed integers a 32 bit systems will have 31 bit for value and 1 bit for sign s0 maximum signed integer range is -2147483648 to 2147483647.