mysql中的数据类型:

整数型:

#查看int整数型的帮助。

mysql> ? intName: '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 schemaNothing foundPlease 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 databaseName: 'CREATE DATABASE'Description:Syntax:CREATE {DATABASE | SCHEMA} [IF NOT EXISTS] db_name    [create_specification] ...create_specification:    [DEFAULT] CHARACTER SET [=] charset_name  | [DEFAULT] COLLATE [=] collation_nameCREATE DATABASE creates a database with the given name. To use thisstatement, you need the CREATE privilege for the database. CREATESCHEMA is a synonym for CREATE DATABASE.URL: http://dev.mysql.com/doc/refman/5.6/en/create-database.html

mysql> ? tinyintName: 'TINYINT'Description:TINYINT[(M)] [UNSIGNED] [ZEROFILL]A very small integer. The signed range is -128 to 127. The unsignedrange is 0 to 255.URL: http://dev.mysql.com/doc/refman/5.6/en/numeric-type-overview.html

mysql> \h intName: '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)