MySQL supports all the standard SQL numeric data types. These
types include the exact numeric data types
(INTEGER,
SMALLINT,
DECIMAL, and
NUMERIC), as well as the
approximate numeric data types
(FLOAT,
REAL, and
DOUBLE PRECISION). The keyword
INT is a synonym for
INTEGER, and the keyword
DEC is a synonym for
DECIMAL. MySQL treats
DOUBLE as a synonym for
DOUBLE PRECISION (a nonstandard
extension). MySQL also treats REAL
as a synonym for DOUBLE PRECISION
(a nonstandard variation), unless the
REAL_AS_FLOAT SQL mode is
enabled.
The data type used for the result of a calculation on numeric
operands depends on the types of the operands and the operations
performed on them. For more information, see
Section 11.6.1, “Arithmetic Operators”.
MySQL Float and Real values do not appear to handle all the IEEE standard floating point representations such as NaN, and +/- Inf. Special accommodations are needed to avoid accidentally inserting 0's for these values when integrating a MySQL database with a scientific application that generates these values.
Posted by Oliver Pereira on February 10 2010 10:28am
Using the MySQL.com search feature to look for documentation on the type BOOL, this page is the highest ranked Reference Manual page that comes up. However, the term does not even appear on the page.
According to the page headed "10.1.1. Overview of Numeric Types", BOOL and BOOLEAN are synonyms for TINYINT(1).
I thought I should include that fact on this page, since the page does come up when searching for it. (Fixing the search feature would be a better solution, though!)
bool deafulting to tinyint is not strict enough. if you really want bool type you should use type "bit(1)" which will allow you to use exactly 1 and 0 and maybe save space or use type "enum('T','F')" which will not save space but make it a true binary flag.
Posted by Miroslav Šustek on October 29 2010 3:22pm
Well, shouldn't a binary type have only two distinct values? (Note that it isn't NULL.)
Explanation from manual (10.4.4. The ENUM Type): ----- If you insert an invalid value into an ENUM (that is, a string not present in the list of permitted values), the empty string is inserted instead as a special error value. This string can be distinguished from a “normal” empty string by the fact that this string has the numeric value 0. More about this later.
If strict SQL mode is enabled, attempts to insert invalid ENUM values result in an error.
Posted by Waheed Alshahnan on November 23 2012 9:39pm
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User Comments
MySQL Float and Real values do not appear to handle all the IEEE standard floating point representations such as NaN, and +/- Inf. Special accommodations are needed to avoid accidentally inserting 0's for these values when integrating a MySQL database with a scientific application that generates these values.
Using the MySQL.com search feature to look for documentation on the type BOOL, this page is the highest ranked Reference Manual page that comes up. However, the term does not even appear on the page.
According to the page headed "10.1.1. Overview of Numeric Types", BOOL and BOOLEAN are synonyms for TINYINT(1).
I thought I should include that fact on this page, since the page does come up when searching for it. (Fixing the search feature would be a better solution, though!)
bool deafulting to tinyint is not strict enough. if you really want bool type you should use type "bit(1)" which will allow you to use exactly 1 and 0 and maybe save space or use type "enum('T','F')" which will not save space but make it a true binary flag.
Be careful when considering ENUM('T','F') as "true binary".
1 row in set (0.00 sec)Example:
CREATE TABLE `bits` (
`val` ENUM('T','F') NOT NULL
);
mysql> INSERT INTO `bits` (`val`) VALUES ('W'), ('T'), ('F');
Query OK, 3 rows affected, 1 warning (0.00 sec)
Records: 3 Duplicates: 0 Warnings: 1
mysql> SHOW WARNINGS;
mysql> SELECT COUNT(DISTINCT val) FROM bits;
1 row in set (0.00 sec)
Well, shouldn't a binary type have only two distinct values?
(Note that it isn't NULL.)
Explanation from manual (10.4.4. The ENUM Type):
-----
If you insert an invalid value into an ENUM (that is, a string not present in the list of permitted values), the empty string is inserted instead as a special error value. This string can be distinguished from a “normal” empty string by the fact that this string has the numeric value 0. More about this later.
If strict SQL mode is enabled, attempts to insert invalid ENUM values result in an error.
There is a know problem when using tinyint(1) and UNION look at bug: #61131
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