mysql有很完善的帮助文档，在mysql命令行下可以通过？ 或者help 加上命令可以查看改命令的帮助信息，
我们查下几个常用的help命令
第一层帮助信息：
？ contents;
mysql> ? 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 Table Maintenance Transactions User-Defined Functions Utility
再查看具体每一层的帮助信息
mysql> ? Account Management;
You asked for help about help category: "Account Management" For more information, type 'help <item>', where <item> is one of the following topics: CREATE USER DROP USER GRANT RENAME USER REVOKE SET PASSWORD mysql> ? Administration You asked for help about help category: "Administration" For more information, type 'help <item>', where <item> is one of the following topics: BINLOG CACHE INDEX CHANGE MASTER TO DEALLOCATE PREPARE EXECUTE STATEMENT FLUSH FLUSH QUERY CACHE HELP COMMAND KILL LOAD INDEX PREPARE PURGE BINARY LOGS RESET RESET MASTER RESET SLAVE SET SET GLOBAL SQL_SLAVE_SKIP_COUNTER SET SQL_LOG_BIN SHOW SHOW AUTHORS SHOW BINARY LOGS SHOW BINLOG EVENTS SHOW CHARACTER SET SHOW COLLATION SHOW COLUMNS SHOW CONTRIBUTORS SHOW CREATE DATABASE SHOW CREATE EVENT SHOW CREATE FUNCTION SHOW CREATE PROCEDURE SHOW CREATE TABLE SHOW CREATE TRIGGER SHOW CREATE VIEW SHOW DATABASES SHOW ENGINE SHOW ENGINES SHOW ERRORS SHOW EVENTS SHOW FUNCTION CODE SHOW FUNCTION STATUS SHOW GRANTS SHOW INDEX SHOW MASTER STATUS SHOW OPEN TABLES SHOW PLUGINS SHOW PRIVILEGES SHOW PROCEDURE CODE SHOW PROCEDURE STATUS SHOW PROCESSLIST SHOW PROFILE SHOW PROFILES SHOW RELAYLOG EVENTS SHOW SLAVE HOSTS SHOW SLAVE STATUS SHOW STATUS SHOW TABLE STATUS SHOW TABLES SHOW TRIGGERS SHOW VARIABLES SHOW WARNINGS START SLAVE STOP SLAVE mysql> ? Compound Statements; You asked for help about help category: "Compound Statements" For more information, type 'help <item>', where <item> is one of the following topics: BEGIN END CASE STATEMENT CLOSE DECLARE CONDITION DECLARE CURSOR DECLARE HANDLER DECLARE VARIABLE FETCH IF STATEMENT ITERATE LEAVE LOOP OPEN REPEAT LOOP RESIGNAL RETURN SELECT INTO SET VARIABLE SIGNAL WHILE mysql> ? Data Definition; You asked for help about help category: "Data Definition" For more information, type 'help <item>', where <item> is one of the following topics: ALTER DATABASE ALTER EVENT ALTER FUNCTION ALTER PROCEDURE ALTER SERVER ALTER TABLE ALTER VIEW CONSTRAINT CREATE DATABASE CREATE EVENT CREATE FUNCTION CREATE INDEX CREATE PROCEDURE CREATE SERVER CREATE TABLE CREATE TRIGGER CREATE VIEW DROP DATABASE DROP EVENT DROP FUNCTION DROP INDEX DROP PROCEDURE DROP SERVER DROP TABLE DROP TRIGGER DROP VIEW MERGE RENAME TABLE TRUNCATE TABLE
这里可以根据不同的分类显示每个分类下支持的mysql指令
mysql> ? START SLAVE;
Name: 'START SLAVE'
Description:
Syntax:
START SLAVE [thread_type [, thread_type] ... ]
START SLAVE [SQL_THREAD] UNTIL
MASTER_LOG_FILE = 'log_name', MASTER_LOG_POS = log_pos
START SLAVE [SQL_THREAD] UNTIL
RELAY_LOG_FILE = 'log_name', RELAY_LOG_POS = log_pos
thread_type: IO_THREAD | SQL_THREAD
START SLAVE with no thread_type options starts both of the slave
threads. The I/O thread reads events from the master server and stores
them in the relay log. The SQL thread reads events from the relay log
and executes them. START SLAVE requires the SUPER privilege.
If START SLAVE succeeds in starting the slave threads, it returns
without any error. However, even in that case, it might be that the
slave threads start and then later stop (for example, because they do
not manage to connect to the master or read its binary log, or some
other problem). START SLAVE does not warn you about this. You must
check the slave's error log for error messages generated by the slave
threads, or check that they are running satisfactorily with SHOW SLAVE
STATUS.
URL: http://dev.mysql.com/doc/refman/5.5/en/start-slave.html
mysql> ? MERGE
Name: 'MERGE'
Description:
The MERGE storage engine, also known as the MRG_MyISAM engine, is a
collection of identical MyISAM tables that can be used as one.
"Identical" means that all tables have identical column and index
information. You cannot merge MyISAM tables in which the columns are
listed in a different order, do not have exactly the same columns, or
have the indexes in different order. However, any or all of the MyISAM
tables can be compressed with myisampack. See
http://dev.mysql.com/doc/refman/5.5/en/myisampack.html. Differences in
table options such as AVG_ROW_LENGTH, MAX_ROWS, or PACK_KEYS do not
matter.
URL: http://dev.mysql.com/doc/refman/5.5/en/merge-storage-engine.html
Examples:
mysql> CREATE TABLE t1 (
-> a INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
-> message CHAR(20)) ENGINE=MyISAM
mysql> CREATE TABLE t2 (
-> a INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
-> message CHAR(20)) ENGINE=MyISAM
mysql> INSERT INTO t1 (message) VALUES ('Testing'),('table'),('t1')
mysql> INSERT INTO t2 (message) VALUES ('Testing'),('table'),('t2')
mysql> CREATE TABLE total (
-> a INT NOT NULL AUTO_INCREMENT,
-> message CHAR(20), INDEX(a))
-> ENGINE=MERGE UNION=(t1,t2) INSERT_METHOD=LAST
mysql> ? create table;
Name: 'CREATE TABLE'
Description:
Syntax:
CREATE [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name
(create_definition,...)
[table_options]
[partition_options]
Or:
CREATE [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name
[(create_definition,...)]
[table_options]
[partition_options]
select_statement
Or:
CREATE [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name
{ LIKE old_tbl_name | (LIKE old_tbl_name) }
create_definition:
col_name column_definition
| [CONSTRAINT [symbol]] PRIMARY KEY [index_type] (index_col_name,...)
[index_option] ...
| {INDEX|KEY} [index_name] [index_type] (index_col_name,...)
[index_option] ...
| [CONSTRAINT [symbol]] UNIQUE [INDEX|KEY]
[index_name] [index_type] (index_col_name,...)
[index_option] ...
| {FULLTEXT|SPATIAL} [INDEX|KEY] [index_name] (index_col_name,...)
[index_option] ...
| [CONSTRAINT [symbol]] FOREIGN KEY
[index_name] (index_col_name,...) reference_definition
| CHECK (expr)
column_definition:
data_type [NOT NULL | NULL] [DEFAULT default_value]
[AUTO_INCREMENT] [UNIQUE [KEY] | [PRIMARY] KEY]
[COMMENT 'string']
[COLUMN_FORMAT {FIXED|DYNAMIC|DEFAULT}]
[reference_definition]
data_type:
BIT[(length)]
| TINYINT[(length)] [UNSIGNED] [ZEROFILL]
| SMALLINT[(length)] [UNSIGNED] [ZEROFILL]
| MEDIUMINT[(length)] [UNSIGNED] [ZEROFILL]
| INT[(length)] [UNSIGNED] [ZEROFILL]
| INTEGER[(length)] [UNSIGNED] [ZEROFILL]
| BIGINT[(length)] [UNSIGNED] [ZEROFILL]
| REAL[(length,decimals)] [UNSIGNED] [ZEROFILL]
| DOUBLE[(length,decimals)] [UNSIGNED] [ZEROFILL]
| FLOAT[(length,decimals)] [UNSIGNED] [ZEROFILL]
| DECIMAL[(length[,decimals])] [UNSIGNED] [ZEROFILL]
| NUMERIC[(length[,decimals])] [UNSIGNED] [ZEROFILL]
| DATE
| TIME
| TIMESTAMP
| DATETIME
| YEAR
| CHAR[(length)]
[CHARACTER SET charset_name] [COLLATE collation_name]
| VARCHAR(length)
[CHARACTER SET charset_name] [COLLATE collation_name]
| BINARY[(length)]
| VARBINARY(length)
| TINYBLOB
| BLOB
| MEDIUMBLOB
| LONGBLOB
| TINYTEXT [BINARY]
[CHARACTER SET charset_name] [COLLATE collation_name]
| TEXT [BINARY]
[CHARACTER SET charset_name] [COLLATE collation_name]
| MEDIUMTEXT [BINARY]
[CHARACTER SET charset_name] [COLLATE collation_name]
| LONGTEXT [BINARY]
[CHARACTER SET charset_name] [COLLATE collation_name]
| ENUM(value1,value2,value3,...)
[CHARACTER SET charset_name] [COLLATE collation_name]
| SET(value1,value2,value3,...)
[CHARACTER SET charset_name] [COLLATE collation_name]
| spatial_type
index_col_name:
col_name [(length)] [ASC | DESC]
index_type:
USING {BTREE | HASH}
index_option:
KEY_BLOCK_SIZE [=] value
| index_type
| WITH PARSER parser_name
| COMMENT 'string'
reference_definition:
REFERENCES tbl_name (index_col_name,...)
[MATCH FULL | MATCH PARTIAL | MATCH SIMPLE]
[ON DELETE reference_option]
[ON UPDATE reference_option]
reference_option:
RESTRICT | CASCADE | SET NULL | NO ACTION
table_options:
table_option [[,] table_option] ...
table_option:
ENGINE [=] engine_name
| AUTO_INCREMENT [=] value
| AVG_ROW_LENGTH [=] value
| [DEFAULT] CHARACTER SET [=] charset_name
| CHECKSUM [=] {0 | 1}
| [DEFAULT] COLLATE [=] collation_name
| COMMENT [=] 'string'
| CONNECTION [=] 'connect_string'
| DATA DIRECTORY [=] 'absolute path to directory'
| DELAY_KEY_WRITE [=] {0 | 1}
| INDEX DIRECTORY [=] 'absolute path to directory'
| INSERT_METHOD [=] { NO | FIRST | LAST }
| KEY_BLOCK_SIZE [=] value
| MAX_ROWS [=] value
| MIN_ROWS [=] value
| PACK_KEYS [=] {0 | 1 | DEFAULT}
| PASSWORD [=] 'string'
| ROW_FORMAT [=] {DEFAULT|DYNAMIC|FIXED|COMPRESSED|REDUNDANT|COMPACT}
| UNION [=] (tbl_name[,tbl_name]...)
partition_options:
PARTITION BY
{ [LINEAR] HASH(expr)
| [LINEAR] KEY(column_list)
| RANGE{(expr) | COLUMNS(column_list)}
| LIST{(expr) | COLUMNS(column_list)} }
[PARTITIONS num]
[SUBPARTITION BY
{ [LINEAR] HASH(expr)
| [LINEAR] KEY(column_list) }
[SUBPARTITIONS num]
]
[(partition_definition [, partition_definition] ...)]
partition_definition:
PARTITION partition_name
[VALUES
{LESS THAN {(expr | value_list) | MAXVALUE}
|
IN (value_list)}]
[[STORAGE] ENGINE [=] engine_name]
[COMMENT [=] 'comment_text' ]
[DATA DIRECTORY [=] 'data_dir']
[INDEX DIRECTORY [=] 'index_dir']
[MAX_ROWS [=] max_number_of_rows]
[MIN_ROWS [=] min_number_of_rows]
[(subpartition_definition [, subpartition_definition] ...)]
subpartition_definition:
SUBPARTITION logical_name
[[STORAGE] ENGINE [=] engine_name]
[COMMENT [=] 'comment_text' ]
[DATA DIRECTORY [=] 'data_dir']
[INDEX DIRECTORY [=] 'index_dir']
[MAX_ROWS [=] max_number_of_rows]
[MIN_ROWS [=] min_number_of_rows]
select_statement:
[IGNORE | REPLACE] [AS] SELECT ... (Some legal select statement)
CREATE TABLE creates a table with the given name. You must have the
CREATE privilege for the table.
Rules for permissible table names are given in
http://dev.mysql.com/doc/refman/5.5/en/identifiers.html. By default,
the table is created in the default database, using the InnoDB storage
engine. An error occurs if the table exists, if there is no default
database, or if the database does not exist.
URL: http://dev.mysql.com/doc/refman/5.5/en/create-table.html
mysql>至于上面一层的命令，我们还可以查看mysql支持的数据类型，
mysql> ? 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> ? Utility; You asked for help about help category: "Utility" For more information, type 'help <item>', where <item> is one of the following topics: DESCRIBE EXPLAIN HELP STATEMENT USE
通过帮助文档还是很方便查到mysql的所有名称，已经每个命令的使用方法和语法。
可以查看mysql内置函数列表，以及每个函数的功能和使用方法：
mysql> ? Functions;
You asked for help about help category: "Functions"
For more information, type 'help <item>', where <item> is one of the following
topics:
PROCEDURE ANALYSE
categories:
Bit Functions
Comparison operators
Control flow functions
Date and Time Functions
Encryption Functions
Information Functions
Logical operators
Miscellaneous Functions
Numeric Functions
String Functions
mysql> ? String Functions;
You asked for help about help category: "String Functions"
For more information, type 'help <item>', where <item> is one of the following
topics:
ASCII
BIN
BINARY OPERATOR
BIT_LENGTH
CAST
CHAR FUNCTION
CHARACTER_LENGTH
CHAR_LENGTH
CONCAT
CONCAT_WS
CONVERT
ELT
EXPORT_SET
EXTRACTVALUE
FIELD
FIND_IN_SET
FORMAT
HEX
INSERT FUNCTION
INSTR
LCASE
LEFT
LENGTH
LIKE
LOAD_FILE
LOCATE
LOWER
LPAD
LTRIM
MAKE_SET
MATCH AGAINST
MID
NOT LIKE
NOT REGEXP
OCTET_LENGTH
ORD
POSITION
QUOTE
REGEXP
REPEAT FUNCTION
REPLACE FUNCTION
REVERSE
RIGHT
RPAD
RTRIM
SOUNDEX
SOUNDS LIKE
SPACE
STRCMP
SUBSTR
SUBSTRING
SUBSTRING_INDEX
TRIM
UCASE
UNHEX
UPDATEXML
UPPER
mysql> ? QUOTE;
Name: 'QUOTE'
Description:
Syntax:
QUOTE(str)
Quotes a string to produce a result that can be used as a properly
escaped data value in an SQL statement. The string is returned enclosed
by single quotation marks and with each instance of backslash ("\"),
single quote ("'"), ASCII NUL, and Control+Z preceded by a backslash.
If the argument is NULL, the return value is the word "NULL" without
enclosing single quotation marks.
URL: http://dev.mysql.com/doc/refman/5.5/en/string-functions.html
Examples:
mysql> SELECT QUOTE('Don\'t!')
-> 'Don\'t!'
mysql> SELECT QUOTE(NULL)
-> NULL
mysql>mysql的插件信息和事务之类的其他信息
mysql> ? Plugins; Name: 'SHOW PLUGINS' Description: Syntax: SHOW PLUGINS SHOW PLUGINS displays information about server plugins. Plugin information is also available in the INFORMATION_SCHEMA.PLUGINS table. See http://dev.mysql.com/doc/refman/5.5/en/plugins-table.html. Example of SHOW PLUGINS output: mysql> SHOW PLUGINS\G *************************** 1. row *************************** Name: binlog Status: ACTIVE Type: STORAGE ENGINE Library: NULL License: GPL *************************** 2. row *************************** Name: CSV Status: ACTIVE Type: STORAGE ENGINE Library: NULL License: GPL *************************** 3. row *************************** Name: MEMORY Status: ACTIVE Type: STORAGE ENGINE Library: NULL License: GPL *************************** 4. row *************************** Name: MyISAM Status: ACTIVE Type: STORAGE ENGINE Library: NULL License: GPL ... URL: http://dev.mysql.com/doc/refman/5.5/en/show-plugins.html mysql> ? Transations; Nothing found Please try to run 'help contents' for a list of all accessible topics mysql> ? Transactions; You asked for help about help category: "Transactions" For more information, type 'help <item>', where <item> is one of the following topics: ISOLATION LOCK SAVEPOINT START TRANSACTION mysql>
通过帮助文档可以查询到mysql的所有命令及每个命令的功能，语法。