在MySQL中帮助的使用主要有以下两个方面：

1 按层次查找帮助：?|help + 类别名称

mysql> ? contents;                #有哪些分类

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

mysql> ? data types                #查看数据有哪些类型

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

mysql> help int;                    #关于数据类型的说明

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.

2 快速查阅帮助

mysql> ? 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.

......

mysql> help 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]

select_statement

CREATE [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name

{ LIKE old_tbl_name | (LIKE old_tbl_name) }

......