MySQL data type

The type of data field defined in MySQL is important for optimizing your database.

MySQL supports multiple types and can be broadly divided into three categories: numeric, date/time, and string (character) types.

Numeric Type

MySQL supports all standard SQL numeric data types.

These types include strict numeric data types (INTEGER, SMALLINT, Decimal, and numeric), as well as 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.

The bit data type holds the bit field values and supports MyISAM, MEMORY, InnoDB, and BDB tables.

As an extension of the SQL standard, MySQL also supports integer types tinyint, Mediumint, and bigint. The following table shows the storage and scope of each integer type that is required.

type	size	Range (signed)	Range (unsigned)	Use
TINYINT	1 bytes	(-128,127)	(0,255)	Small integer value
SMALLINT	2 bytes	(-32 768,32 767)	(0,65 535)	Large integer value
Mediumint	3 bytes	(-8 388 608,8 388 607)	(0,16 777 215)	Large integer value
int or integer	4 bytes	(-2 147 483 648,2 147 483 647)	(0,4 294 967 295)	Large integer value
BIGINT	8 bytes	(-9 233 372 036 854 775 808,9 223 372 036 854 775 807)	(0,18 446 744 073 709 551 615)	Maximum integer value
FLOAT	4 bytes	( -3.402 823 466 e+38,1.175 494 351 E-38), 0, (1.175 494 351 e-38,3.402 823 466 351 e+38)	0, (1.175 494 351 e-38,3.402 823 466 e+38)	Single precision Floating point value
DOUBLE	8 bytes	(1.797 693 134 862 315 7 e+308,2.225 073 858 507 201 4 E-308), 0, (2.225 073 858 507 201 4 e-308,1.797 693 134 862 315 7 e+3 08)	0, (2.225 073 858 507 201 4 e-308,1.797 693 134 862 315 7 e+308)	Double precision Floating point value
DECIMAL	For decimal (m,d), if m>d, is m+2 otherwise d+2	Values that depend on M and D	Values that depend on M and D	Decimal value

date and Time type

The date and time types that represent time values are datetime, date, TIMESTAMP, hour, and year.

Each time type has a valid value range and a value of "0", and a value of "0" is used when specifying an illegal MySQL value that cannot be represented.

The timestamp type has a proprietary Automatic Update feature, which is described later.

type	size (bytes)	Range	format	Use
DATE	3	1000-01-01/9999-12-31	Yyyy-mm-dd	Date value
Time	3	' -838:59:59 '/' 838:59:59 '	HH:MM:SS	Time Value or duration
Year	1	1901/2155	YYYY	Year value
Datetime	8	1000-01-01 00:00:00/9999-12-31 23:59:59	YYYY-MM-DD HH:MM:SS	Blend date and time values
TIMESTAMP	8	1970-01-01 00:00:00/2037, sometime	YYYYMMDD HHMMSS	Mixed date and time values, timestamp

String Type

The string type refers to Char, VARCHAR, BINARY, VARBINARY, BLOB, TEXT, enum, and set. This section describes how these types work and how they are used in queries.

type	size	purpose
CHAR	0-255 bytes	fixed length string
VARCHAR	0-65535 bytes	variable length string
tinyblob	0-255 bytes	No more than 255 characters in a binary string
tinytext	0-255 bytes	short text string
BLOB	0-65 535 bytes	long text data in binary form
text	0-65 535 bytes	long text data
mediumblob	0-16 777 215-byte	medium-length text data in binary form
mediumtext	0-16 777 215 bytes	medium-length text data
logngblob	0-4 294 967 295 bytes	binary form of great text data
LO Ngtext	0-4 294 967 295 bytes	great text data

Char and varchar types are similar, but they are saved and retrieved in different ways. They are also different in terms of their maximum length and whether trailing spaces are retained. No case conversions are made during the storage or retrieval process.

Binary and varbinary classes are similar to char and varchar, but they contain binary strings rather than binary strings. That is, they contain a byte string instead of a character string. This means that they do not have a character set, and sort and compare numeric values based on column-valued bytes.

A blob is a binary large object that can hold a variable amount of data. There are 4 types of blobs: Tinyblob, BLOBs, Mediumblob, and Longblob. They can only accommodate the maximum length of a value differently.

There are 4 types of text: Tinytext, text, Mediumtext, and Longtext. These correspond to 4 types of blobs, with the same maximum length and storage requirements.

Original address: http://www.manongjc.com/mysql/mysql_data_types.html

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