mysql中的数据类型：

整数型：

#查看int整数型的帮助。mysql> ? int

Name: 'INT'

Description:

INT[(M)] [UNSIGNED] [ZEROFILL]

A normal-size integer. The signed range is -2147483648 to 2147483647.

The unsigned range is 0 to 4294967295.

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

#查看创建数据库的帮助，这块发现使用schema不识别。mysql> help create schema

Nothing found

Please try to run 'help contents' for a list of all accessible topics

#可以使用help ？ \h 三选一查看帮助。mysql> help create database

Name: 'CREATE DATABASE'

Description:

Syntax:

CREATE {DATABASE | SCHEMA} [IF NOT EXISTS] db_name

[create_specification] ...

create_specification:

[DEFAULT] CHARACTER SET [=] charset_name

| [DEFAULT] COLLATE [=] collation_name

CREATE DATABASE creates a database with the given name. To use this

statement, you need the CREATE privilege for the database. CREATE

SCHEMA is a synonym for CREATE DATABASE.

URL: http://dev.mysql.com/doc/refman/5.6/en/create-database.html

mysql> ? tinyint

Name: 'TINYINT'

Description:

TINYINT[(M)] [UNSIGNED] [ZEROFILL]

A very small integer. The signed range is -128 to 127. The unsigned

range is 0 to 255.

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

mysql> \h int

Name: 'INT'

Description:

INT[(M)] [UNSIGNED] [ZEROFILL]

A normal-size integer. The signed range is -2147483648 to 2147483647.

The unsigned range is 0 to 4294967295.

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

浮点类型：

M是数字总位数，D是小数点后面的位数。

float(M,D)

字符串类型：

char(M) M个字节，0-255

varchar(M) L+1个字节，0-65535

日期时间类型：

time

date

datetime

year

#查看mysql有那些存储引擎(默认是innodb)mysql> show engines;

+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+

| Engine             | Support | Comment                                                        | Transactions | XA   | Savepoints |

+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+

| MEMORY             | YES     | Hash based, stored in memory, useful for temporary tables      | NO           | NO   | NO         |

| CSV                | YES     | CSV storage engine                                             | NO           | NO   | NO         |

| MRG_MYISAM         | YES     | Collection of identical MyISAM tables                          | NO           | NO   | NO         |

| BLACKHOLE          | YES     | /dev/null storage engine (anything you write to it disappears) | NO           | NO   | NO         |

| MyISAM             | YES     | MyISAM storage engine                                          | NO           | NO   | NO         |

| FEDERATED          | NO      | Federated MySQL storage engine                                 | NULL         | NULL | NULL       |

| ARCHIVE            | YES     | Archive storage engine                                         | NO           | NO   | NO         |

| InnoDB             | DEFAULT | Supports transactions, row-level locking, and foreign keys     | YES          | YES  | YES        |

| PERFORMANCE_SCHEMA | YES     | Performance Schema                                             | NO           | NO   | NO         |

+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+

9 rows in set (0.00 sec)

#查看显示支持的存储引擎的信息：mysql> show variables like 'have%';

+----------------------+----------+

| Variable_name        | Value    |

+----------------------+----------+

| have_compress        | YES      |

| have_crypt           | YES      |

| have_dynamic_loading | YES      |

| have_geometry        | YES      |

| have_openssl         | DISABLED |

| have_profiling       | YES      |

| have_query_cache     | YES      |

| have_rtree_keys      | YES      |

| have_ssl             | DISABLED |

| have_symlink         | DISABLED |

+----------------------+----------+

10 rows in set (0.00 sec)