I was wondering if I can set a max value in column definition of MySQL, just like we set a default value during column definition. If it can be done, how can it be achieved ? Example format:
int(5) not null default 1 <Something to set max value> ??
In table definition, you can only specify maximum number of characters, for example, when you specify a column as int(5), you are limiting the field to 5 bits.
Please refer to the documentation.
To make sure the column will not accept an integer greather that 50 for exeample, you will need to use triggers for example:
CREATE TRIGGER check_trigger
BEFORE INSERT
ON table
FOR EACH ROW
BEGIN
IF NEW.age<0 OR NEW.age>50 THEN
CALL `Error: Wrong values for age`; -- this trick will throw an error
END IF;
END
You can only control the max values of a column by changing the type.
If your minimum value desired is -128 and your max required is 127, then you can go with a TINYINT(). If you need between -32768 and 32767, then you need a SMALLINT(), and so on.
Source: MySQL Docs: Integer Types (Exact Value) - INTEGER, INT, SMALLINT, TINYINT, MEDIUMINT, BIGINT
Presuming you are dealing with "max" and "min" integers, for instance...
TINYINT : 1 byte, -128 to 127 signed, 0 to 255 unsigned
SMALLINT : 2 bytes, -32768 to 32767 signed, 0 to 65535 unsigned
MEDIUMINT : 3 bytes, -8388608 to 8388607 signed, 0 to 16777215 unsigned
INT : 4 bytes, -2147483648 to 2147483647 signed, 0 to 4294967295 unsigned
BIGINT : 8 bytes, -2^63 to 2^63-1 signed, 0 to 2^64-1 unsigned
Related
Ok, so I know that the INT type in MySQL has a range of either 0 to 4,294,967,295 or of -2,147,483,648 to 2,147,483,647
MySQL reference
My question is if I have a single row in an INT column with a value of -1 and all other rows are positive numbers, what is the actual range of that column? Because it has a single negative number, does the column automatically have a range of -2,147,483,648 to 2,147,483,647, or is the range more dynamic and instead is -1 to 4,294,967,294?
So to be more specific about the INT datatype; you can have either INT UNSIGNED or INT SIGNED. This is set when the column is created. I believe it defaults to SIGNED if you don't specify. So any INT column is either SIGNED or UNSIGNED and this is NOT dynamic.
INT UNSIGNED has the range 0 to 4,294,967,295
INT SIGNED has the range -2,147,483,648 to 2,147,483,647
So if even one row has a negative value, you have to use INT SIGNED. Giving the column the range -2,147,483,648 to 2,147,483,647.
The ranges you are seeing in the MySQL reference are describing whether or not you add in SIGNED (the default if left blank) or UNSIGNED as an attribute in your column definition. E.g., CREATE TABLE my_table(column_1 INT UNSIGNED...).
If you specify UNSIGNED you extend the upper bound of the data type (assuming the data type in question has a SIGNED/UNSIGNED option), but you also lose the lower end of the range. If you specify SIGNED or don't specify anything at all (then the default SIGNED will apply) then your upper bound is the upper bound of the SIGNED range.
So, for a SIGNED column of type INT (or if no attribute is specified), your range is -2,147,483,648 to 2,147,483,647. If you specify UNSIGNED your range is 0 to 4,294,967,295, and you would not actually be able to put -1 in that column and have it be properly stored as -1. Per http://dev.mysql.com/doc/refman/5.1/en/out-of-range-and-overflow.html, MySQL "stores the value representing the corresponding endpoint of that range" for integers. So inserting -1 into an UNSIGNED integer column will store 0 instead. If you need to store negative integer values, you need to use SIGNED. If you need an extended upper range and don't need to store negative numbers, you would want to use the UNSIGNED attribute.
The range of 0 to 4,294,967,295 is for UNSIGNED. As an example:
...
`type` int(10) UNSIGNED NOT NULL DEFAULT '0'
...
You have to specifically set the unsigned state for the column otherwise it is considered signed which will have the range of -2,147,483,648 to 2,147,483,647
No, the ranges are not dynamically adjusted to the filled data. SIGNED and UNSIGNED ranges are raw ranges, regardless what the table already contains.
CREATE TABLE `testing` (
`x` INT(11) NULL DEFAULT NULL
)
ENGINE=InnoDB
;
INSERT INTO testing VALUES (-1);
SELECT * FROM testing;
INSERT INTO testing VALUES (4000000000);
SELECT * FROM testing;
Returns "Out of range error", and data will be "-1 ; 2147483647" (greatest SIGNED INT 32 bits)
I read the answers given here: What is the difference between tinyint, smallint, mediumint, bigint and int in MySQL? , so I now know how they store the data, but I'm still not sure how to set my database up. For example, if I want a field to be either 0 or 1 (sort of binary, 0 = off, 1 = on), do I use TINYINT with a length of 1?
My main question is, what does the LENGTH setting determine? As each NUMERIC data type already has their own associated data size.
Also, what is the difference between SIGNED and UNSIGNED, and why should I choose one over the other?
http://dev.mysql.com/doc/refman/5.0/en/numeric-type-overview.html
Diffrence between SIGNED and UNSIGNED is with UNSIGNED you can store only positive numbers.
For example :
about INT (Normal INTEGER) values
The signed range is -2147483648 to 2147483647. The unsigned range is 0 to 4294967295.
If you are using PK auto_increment value then you should use UNSIGNED in this case.
http://dev.mysql.com/doc/refman/5.0/en/integer-types.html
This shows storage and range for each INTEGER types.
For binary fields use BIT.
the length of numerics specifies the precision before and after the comma. See here
An integer variable has 32 bits to store the integer value.
In signed integer the first bit is reserved to store positive or negative sign. So, a signed integer can use only 31 bits to store a value and hence its range will be −2,147,483,648 to +2,147,483,647.
Suppose if your program needs to store only positive integer greater than +2,147,483,647. You need to consider the long integer that will take 8 bits that will cause the wastage of memory.
Instead you can go with unsigned integer. In an unsigned integer no bit is reserved for the sign so now you have 32 bits to store the value. The only limitation with an unsigned integer is that you cannot use it to store negative values. The range of an unsigned integer of 32 bits will be 0 to 4,294,967,295.
Hope it clears your concept of signed and unsigned integer.
I have a mysql database in which i am using auto_increment(integer), can you tell me till what integer it can incremented. How we can increase the limit of auto_increment?
The limit of an auto_increment column is the size of the column:
Use a large enough integer data type for the AUTO_INCREMENT column to hold the maximum sequence value you will need. When the column reaches the upper limit of the data type, the next attempt to generate a sequence number fails. For example, if you use TINYINT, the maximum permissible sequence number is 127. For TINYINT UNSIGNED, the maximum is 255.
The limits of the integer types are:
TINYINT - 127
UNSIGNED TINYINT - 255
SMALLINT - 32767
UNSIGNED SMALLINT - 65535
MEDIUMINT - 8388607
UNSIGNED MEDIUMINT - 16777215
INT - 2147483647
UNSIGNED INT - 4294967295
BIGINT - 9223372036854775807
UNSIGNED BIGINT - 18446744073709551615
Integer can go as high as 2147483647. If unsigned it can be 4294967295.
See this chart for all of the integer values.
I'm under the assumption that INT(1) is the exact same thing as TINYINT(1) but I really have no idea. Whenever I've had values that can only be a single integer (e.g. a value 0-9), I've always just used INT(1) to say it's an integer and it will only be one character, which I assume means that it could only be a value 0 through 9 (please explain this to me if I'm wrong). I've always just ignored the other types of INT that you can cast the number as. I'm no MySQL savvy and tend to avoid the more complicated things you can do with it.
So my question, is there any difference between the various integer types INT, TINYINT, SMALLINT, MEDIUMINT, and BIGINT if you define a length of 1 for each type;? If not, should I use them anyways (I can see using them for more semantic meaning, TINYINT being more specific than just INT)? If so, could I easily (and/or should I) just go through my database and change all my INT(1) fields to TINYINT(1) fields?
Here you'll understand it in a better way!
tinyint: 1 byte, -128 to +127 / 0 to 255 (unsigned)
smallint: 2 bytes, -32,768 to +32,767 / 0 to 65,535 (unsigned)
mediumint: 3 bytes, -8,388,608 to 8,388,607 / 0 to 16,777,215 (unsigned)
int/integer: 4 bytes, -2,147,483,648 to +2,147,483,647 / 0 to 4,294,967,295 (unsigned)
bigint: 8 bytes, -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807 / 0 to 18,446,744,073,709,551,615 (unsigned)
The number in parentheses for integer column types is the "display width". This does not effect the storage requirements as they are pre-defined.
Further reading
http://dev.mysql.com/doc/refman/5.0/en/data-types.html
http://dev.mysql.com/doc/refman/5.0/en/numeric-types.html
To summarize the accepted answered :
The number in parentheses indicates the *number of characters to display that field*, **not** the storage size of the field.
But if you want to know the storage size, you should check the MySQL source documents.
Source: MySQL Docs: Integer Types (Exact Value) - INTEGER, INT, SMALLINT, TINYINT, MEDIUMINT, BIGINT
Direct quote from source documentation :
TINYINT : 1 byte, -128 to 127 signed, 0 to 255 unsigned
SMALLINT : 2 bytes, -32768 to 32767 signed, 0 to 65535 unsigned
MEDIUMINT : 3 bytes, -8388608 to 8388607 signed, 0 to 16777215 unsigned
INT : 4 bytes, -2147483648 to 2147483647 signed, 0 to 4294967295 unsigned
BIGINT : 8 bytes, -2^63 to 2^63-1 signed, 0 to 2^64-1 unsigned
What's the difference in int(11) and int(11) UNSIGNED ?
An UNSIGNED type cannot be negative, but on the other hand it has twice as large a range for the positive integers. The types TINYINT, SMALLINT, MEDIUMINT,
INT and BIGINT all have signed and unsigned versions.
For INT the ranges are defined as follows:
Type Storage Min Max
INT 4 -2147483648 2147483647
INT UNSIGNED 4 0 4294967295
The signed and unsigned types take the same storage space (4 bytes for INT).
See the documentation for more details.
INT goes from -2147483648 to +2147483647
UNSIGNED INT goes from 0 to 4294967295
the 11 between the braces has no effect on the number, just how it's displayed.
UNSIGNED means that it can hold only nonnegative values, i.e. it can't hold for example -20
UNSIGNED is exactly that, its all positive (no sign) numbers. The size of bytes is the same, but if your data is never negative you can get larger positive numbers out of it. The 11 is the default of how many characters it will fetch and display. For the exact size, do a search for the DBMS you are using and the type.
All integer types can have an optional (nonstandard) attribute UNSIGNED. Unsigned type can be used to permit only nonnegative numbers in a column or when you need a larger upper numeric range for the column. For example, if an INT column is UNSIGNED, the size of the column's range is the same but its endpoints shift from -2147483648 and 2147483647 up to 0 and 4294967295.
see here: http://dev.mysql.com/doc/refman/5.0/en/numeric-types.html
The unsigned one can't hold negative numbers.
An unsigned integer can handle values from 0 to 2^(size in bits of the integer field). A signed integer can handle values from -2^(size of the integer field-1) to 2^(size of the integer field-1)-1.
I think you may want to know the difference between int and int(10).
Let's give an example for int(10) one with zerofill keyword, one not, the table likes that:
create table tb_test_int_type(
int_10 int(10),
int_10_with_zf int(10) zerofill,
unit int unsigned
);
Let's insert some data:
insert into tb_test_int_type(int_10, int_10_with_zf, unit)
values (123456, 123456,3147483647), (123456, 4294967291,3147483647)
;
Then
select * from tb_test_int_type;
# int_10, int_10_with_zf, unit
'123456', '0000123456', '3147483647'
'123456', '4294967291', '3147483647'
We can see that
with keyword zerofill, num less than 10 will fill 0, but without zerofill it won't
Secondly with keyword zerofill, int_10_with_zf becomes unsigned int type, if you insert a minus you will get error Out of range value for column...... But you can insert minus to int_10. Also if you insert 4294967291 to int_10 you will get error Out of range value for column.....
Conclusion:
int(X) without keyword zerofill, is equal to int range -2147483648~2147483647
int(X) with keyword zerofill, the field is equal to unsigned int range 0~4294967295, if num's length is less than X it will fill 0 to the left