MySQL数据类型

MySQL数据库提供了整数类型，浮点类型，定点数类型，位类型， 日期和时间类型，字符串类型

数据类型	字节	最小值	最大值
TINYINT	1	有符号 -128，无符号 0	有符号127，无符号 255
SMALLINT	2	有符号 -32768 无符号 0	有符号 32767 无符号 32767 *2+ 1
MEDIUMINT	3	有符号 -8388608 无符号 0	有符号 8388607无符号 8388607*2 + 1
INT	4	有符号 -2147483648 无符号 0	有符号 -21474836487无符号 21474836487*2 + 1
BIGINT	8	有符号 -9223372036854775808 无符号 0	有符号 -9223372036854775807 无符号 922337206854775807 * 2+ 1
FLOAT	4	+- 1.75494351E-38	+- -3.402823466E+38
DOUBLE	8	+- 2.2250738585072014E-308	+- 1.7976931348623157E+308
DEC(M,D) DECIMAL(M,D)	M+2	同double	同double
BIT	1~8	1 bit	64 bit
DATE 年月日	4	1000-01-01	9999-12-31
DATETIME 年月日时分秒	8	1000-01-01 00:00:00.000000	9999-12-31 23:59:59.999999
TIMESTAMP 当前系统时间	4	1970-01-01 00:00:01.000000	2038-01-19 03:14:07.999999
TIME 时分秒	3	-838:59:59.000000	838:59:59.000000
YEAR 年份	1	1000	9999
CHAR(M)	M
VARCHAR(M)	M
TINYTEXT	0~255
TEXT	0~65535
MEDIUMTEXT	0~ 16,777,215
LONGTEXT	0~4,294,967,295
BINARY(M)
VARBINARY(M)
TINYBLOB
BLOB
MEDIUMBLOB
LONGBLOB

这么多的数据类型谁记得住啊，不用记住，几个命令，现场查看：

HELP：

mysql> help Contents;
You asked for help about help category: "Contents"
For more information, type 'help <item>', where <item> is one of the following
categories:
   Account Management
   Administration
   Compound Statements
   Data Definition
   Data Manipulation
   Data Types
   Functions
   Functions and Modifiers for Use with GROUP BY
   Geographic Features
   Help Metadata
   Language Structure
   Plugins
   Procedures
   Storage Engines
   Table Maintenance
   Transactions
   User-Defined Functions
   Utility

mysql> help Data Types;
You asked for help about help category: "Data Types"
For more information, type 'help <item>', where <item> is one of the following
topics:
   AUTO_INCREMENT
   BIGINT
   BINARY
   BIT
   BLOB
   BLOB DATA TYPE
   BOOLEAN
   CHAR
   CHAR BYTE
   DATE
   DATETIME
   DEC
   DECIMAL
   DOUBLE
   DOUBLE PRECISION
   ENUM
   FLOAT
   INT
   INTEGER
   LONGBLOB
   LONGTEXT
   MEDIUMBLOB
   MEDIUMINT
   MEDIUMTEXT
   SET DATA TYPE
   SMALLINT
   TEXT
   TIME
   TIMESTAMP
   TINYBLOB
   TINYINT
   TINYTEXT
   VARBINARY
   VARCHAR
   YEAR DATA TYPE

mysql> help date;  -- 哪里不会查哪里
Name: 'DATE'
Description:
DATE

A date. The supported range is '1000-01-01' to '9999-12-31'. MySQL
displays DATE values in 'YYYY-MM-DD' format, but permits assignment of
values to DATE columns using either strings or numbers.

URL: http://dev.mysql.com/doc/refman/5.6/en/date-and-time-type-overview.html

可以查看的不止是数据类型，关于MySQL的一切使用帮助。