如何使用 MySQL 安装后自带的帮助文档

一、查询帮助文档

输入命令 ? contents 或者 help contents 来显示所有可供查询的分类：

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

接着，你可以继续查询相关的分类，例如查看数据库支持的数据类型，可以输入命令 ? data types：

mysql> ? data types;
You asked for help about help category: "Data Types"
For more information, type 'help ', where  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

如果想知道 int 类型的具体介绍，可以输入命令 ? int：

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

查看数据库的函数分类，输入命令 ? functions：

mysql> ? functions;
You asked for help about help category: "Functions"
For more information, type 'help ', where  is one of the following
categories:
   Bit Functions
   Comparison Operators
   Control Flow Functions
   Date and Time Functions
   Encryption Functions
   GROUP BY Functions and Modifiers
   Information Functions
   Locking Functions
   Logical Operators
   Miscellaneous Functions
   Numeric Functions
   Spatial Functions
   String Functions

查看某个具体函数的使用说明，例如查看ifnull函数的使用说明，输入命令 ? ifnull：

mysql> ? ifnull;
Name: 'IFNULL'
Description:
Syntax:
IFNULL(expr1,expr2)

If expr1 is not NULL, IFNULL() returns expr1; otherwise it returns
expr2.

URL: https://dev.mysql.com/doc/refman/5.6/en/control-flow-functions.html

Examples:
mysql> SELECT IFNULL(1,0);
        -> 1
mysql> SELECT IFNULL(NULL,10);
        -> 10
mysql> SELECT IFNULL(1/0,10);
        -> 10
mysql> SELECT IFNULL(1/0,'yes');
        -> 'yes'

查看数据库命令的详细说明，例如查看命令 show 的使用说明，输入命令 ? show：

mysql> ? show;
Name: 'SHOW'
Description:
SHOW has many forms that provide information about databases, tables,
columns, or status information about the server. This section describes
those following:

SHOW AUTHORS
SHOW {BINARY | MASTER} LOGS
SHOW BINLOG EVENTS [IN 'log_name'] [FROM pos] [LIMIT [offset,] row_count]
SHOW CHARACTER SET [like_or_where]
SHOW COLLATION [like_or_where]
SHOW [FULL] COLUMNS FROM tbl_name [FROM db_name] [like_or_where]
SHOW CONTRIBUTORS
SHOW CREATE DATABASE db_name
SHOW CREATE EVENT event_name
SHOW CREATE FUNCTION func_name
SHOW CREATE PROCEDURE proc_name
SHOW CREATE TABLE tbl_name
SHOW CREATE TRIGGER trigger_name
SHOW CREATE VIEW view_name
SHOW DATABASES [like_or_where]
SHOW ENGINE engine_name {STATUS | MUTEX}
SHOW [STORAGE] ENGINES
SHOW ERRORS [LIMIT [offset,] row_count]
SHOW EVENTS
SHOW FUNCTION CODE func_name
SHOW FUNCTION STATUS [like_or_where]
SHOW GRANTS FOR user
SHOW INDEX FROM tbl_name [FROM db_name]
SHOW MASTER STATUS
SHOW OPEN TABLES [FROM db_name] [like_or_where]
SHOW PLUGINS
SHOW PROCEDURE CODE proc_name
SHOW PROCEDURE STATUS [like_or_where]
SHOW PRIVILEGES
SHOW [FULL] PROCESSLIST
SHOW PROFILE [types] [FOR QUERY n] [OFFSET n] [LIMIT n]
SHOW PROFILES
SHOW RELAYLOG EVENTS [IN 'log_name'] [FROM pos] [LIMIT [offset,] row_count]
SHOW SLAVE HOSTS
SHOW SLAVE STATUS
SHOW [GLOBAL | SESSION] STATUS [like_or_where]
SHOW TABLE STATUS [FROM db_name] [like_or_where]
SHOW [FULL] TABLES [FROM db_name] [like_or_where]
SHOW TRIGGERS [FROM db_name] [like_or_where]
SHOW [GLOBAL | SESSION] VARIABLES [like_or_where]
SHOW WARNINGS [LIMIT [offset,] row_count]

like_or_where:
    LIKE 'pattern'
  | WHERE expr

If the syntax for a given SHOW statement includes a LIKE 'pattern'
part, 'pattern' is a string that can contain the SQL % and _ wildcard
characters. The pattern is useful for restricting statement output to
matching values.

Several SHOW statements also accept a WHERE clause that provides more
flexibility in specifying which rows to display. See
https://dev.mysql.com/doc/refman/5.6/en/extended-show.html.

URL: https://dev.mysql.com/doc/refman/5.6/en/show.html

如果想查看 create table 的语法, 可以使用以下命令 create table：

mysql> ? create table;
Name: 'CREATE TABLE'
Description:
Syntax:
CREATE [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name
    (create_definition,...)
    [table_options]
    [partition_options]

CREATE [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name
    [(create_definition,...)]
    [table_options]
    [partition_options]
    [IGNORE | REPLACE]
    [AS] query_expression

CREATE [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name
    { LIKE old_tbl_name | (LIKE old_tbl_name) }

create_definition:
    col_name column_definition
  | {INDEX|KEY} [index_name] [index_type] (key_part,...)
      [index_option] ...
  | {FULLTEXT|SPATIAL} [INDEX|KEY] [index_name] (key_part,...)
      [index_option] ...

二、MySQL 相关资源网址

https://dev.mysql.com/downloads/：是MySQL的官方网站, 可以下载到各个版本的MySQL以及相关客户端开发工具等. https://dev.mysql.com/doc/：提供了目前最权威的MySQL数据库及工具的在线手册 https://bugs.mysql.com/：这里可以查看到MySQL已经发布的bug列表, 或者向MySQL提交bug报告 https://www.mysql.com/news-and-events/newsletter/：通常会发布各种关于MySQL的最新消息.