I always thought INT(5) means a number which has a max size of 5 digits. I tried entering a huge number inside it and it somehow got cut down to 2147483647
This obviously isnt 5 digits. So what does INT(5) have a limitation of ?
From MySQL Docs, Numeric Type Attributes
MySQL supports an extension for optionally specifying the display width of integer data types in parentheses following the base keyword for the type. For example, INT(4) specifies an INT with a display width of four digits. This optional display width may be used by applications to display integer values having a width less than the width specified for the column by left-padding them with spaces. (That is, this width is present in the metadata returned with result sets. Whether it is used or not is up to the application.)
INT is always four bytes wide. The 5 is the "display width".
In MySQL, INT(5) does not mean that values are limited to 5-character values. It only means that MySQL will try to pad these values with spaces/zeroes when returning them.
The numeric range of any signed INT including INT(10), INT(5) or any other INT(n) is:
-2,147,483,648 ... 2,147,483,647, which is 10 digits at most.
http://dev.mysql.com/doc/refman/5.0/en/numeric-type-overview.html
"M indicates the maximum display width for integer types. The maximum legal display width is 255. Display width is unrelated to the range of values a type can contain, as described in Section 10.2, “Numeric Types”"
https://alexander.kirk.at/2007/08/24/what-does-size-in-intsize-of-mysql-mean/
M indicates the maximum display width for integer types. For floating-point and fixed-point types, M is the total number of digits that can be stored. For string types, M is the maximum length. The maximum allowable value of M depends on the data type.
An int can be between -2147483648 and 2147483647 signed, or 0 and 4294967295 unsigned.
Thats why it was cut down to that if you entered a number larger than it as a signed value
A very common misconception about what int(N) means in MySQL is that the column can store maximum integer value with N digits in length. However, this is not true. int(N) does not determines the maximum value that the column can store in it. N is the display width of the integer column, unlike the characters columns where the number means number of character that can be stored.
The number in the parenthesis does not determines the max and min values that can be stored in the integer field. The max and min values that can be stored are always fixed. The following table shows the required storage and range for each integer type.
Related
Why do we have the limitation on datatypes like Char and varchar etc. but not on Integer ?
Why its designed in such a way ?
Eg:
We can define char(8), but we cannot define Int(8) or integer(8). It would have a max of 11 characters saved for it.
Integer have a fixed size of bytes 1-8, depending which kind you have defined.
char has a fixed size of bytes per character so you defined the size of 8 character you get 8 times the size if the character.
As it makes no sense to limit that fixed size if bytes, mysqkl finally kicked it out(in future) and gives now a warning, when you create a integer with a size
I want to store a field which stores channel clicks per day( increasing every second and updated in a day) into MySQL DB table. What datatype should I assign to the column keeping in mind that it can even be less than 100 or can even exceed a million.
MySQL Integer Types (Exact Value):
Fixed-Point Types (Exact Value) - DECIMAL, NUMERIC:
In standard SQL, the syntax DECIMAL(M) is equivalent to DECIMAL(M,0).
Similarly, the syntax DECIMAL is equivalent to DECIMAL(M,0), where the
implementation is permitted to decide the value of M. MySQL supports
both of these variant forms of DECIMAL syntax. The default value of M
is 10.
If the scale is 0, DECIMAL values contain no decimal point or
fractional part.
The maximum number of digits for DECIMAL is 65, but the actual range
for a given DECIMAL column can be constrained by the precision or
scale for a given column. When such a column is assigned a value with
more digits following the decimal point than are permitted by the
specified scale, the value is converted to that scale. (The precise
behavior is operating system-specific, but generally the effect is
truncation to the permissible number of digits.)
Storage Requirements:
I created two fields text(varchar), number(int) using mysql. But I am not sure what size i should put for varchar(), int() , for varchar(), I checked here: http://dev.mysql.com/doc/refman/5.0/en/char.html, and know if I put varchar(4), it means: can hold up to 4 characters. But for int(4), I checked here: http://dev.mysql.com/doc/refman/5.0/en/integer-types.html, It is said: Maximum Value:(Signed/Unsigned)(2147483647/4294967295)
Question:
for int(4), how did it get this value2147483647/4294967295? if i put int(8), what would the value be?
See the MySQL Numeric Type Documentation. These things are well-documented.
The range for a signed INT is [-2147483648, 2147483647].
Note that in the case of INT(x), x is the "display width" and has nothing to do with the range or space requirements:
MySQL supports an extension for optionally specifying the display width of integer data types in parentheses following the base keyword for the type. For example, INT(4) specifies an INT with a display width of four digits ... display width does not constrain [or expand] the range of values that can be stored in the column.
Mysql int(11) number out of range
int(4) an INT with a display width of four digits.
int(8) an INT with a display width of eight digits.
Minimum Value/Maximum Value are the same for an int type which use 4 bytes to storage.
-2147483648 to 2147483647 for signed, and 0 to 4294967296 for unsigned.
Well, from the browser console I note:
Math.pow(2, 4*8) is 4294967296 and half that is 2147483648
those are 1 off the maximum (unsigned/signed) integer that can be stored in binary form using 4 8-bit bytes.
What is the difference between BIT and BOOLEAN?
tinyint(1) is an integer type with a defined display width of 1. The BIT data type represents bit-field values which can have from 1 to 64 bits.
The storage size of tinyint is always 1 byte while the storage size of BIT(n) is approximately INT((n+7)/8) bytes
You can write to a BIT field using a special notation e.g. b'1111', don't think you can use this with INT/TINYINT fields
I've used MySQL (via PHPMyAdmin) a lot before but never really understood half of it. I'm assuming that for varchar, length is the maximum length of a string that can go there. But what about for Int? According to this, Int is a 4 byte integer, so why have a Length parameter for it? Is it the number of bits for that integer? Why have seperate numeric types when you can just specify the size of Int? What about for other data types?
For numeric types, the size is neither bits nor bytes. It's just the display width, that is used when the field has ZEROFILL specified.
Source: http://alexander.kirk.at/2007/08/24/what-does-size-in-intsize-of-mysql-mean/