MySQL帮助文档的使用

超、凢脫俗 2021-12-10 12:39 309阅读 0赞

# 帮助文档使用 #

在 MySQL 使用过程中，可能经常会遇到以下问题：

*  某个操作语法忘记了，需要快速查找。
 *  当前版本上，某个字段类型我们想快速知道它的取值范围？
 *  当前版本上，都支持哪些函数？希望有例子能快速入门。
 *  当前版本上，是否支持某个功能？

对于上面列出的各种问题，我们可能想到的办法是查找 MySQL 的文档。不错，这些问题在 MySQL 官方文档中都可以很清楚地查到，但是却要耗费大量的时间和精力。 所以对于以上问题，最好的解决办法是使用 MySQL 安装后自带的帮助文档，这样在遇到问 题时就可以方便快捷地进行查询。

1.  按照层次看帮助
    
    如果不知道帮助能够提供些什么，可以用“？contents”命令来显示所有可供查询的的分类， 如下例所示：
    
        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
           Procedures
           Storage Engines
           Table Maintenance
           Transactions
           User-Defined Functions
           Utility
    
    对于列出的分类，可以使用“? 类别名称”的方式针对用户感兴趣的内容做进一步的查看。 例如，想看看 MySQL 中都支持哪些数据类型，可以执行“? data types”命令：
    
        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
    
    上面列出的此版本支持的所有数据类型，如果想知道int类型的具体介绍，也可以使用上忙的方法，做进一步的查看：
    
        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
    
    帮助文档中显示了 int 类型的详细描述。通过这种“？ 类别名称”的方式，就可以一层层 地往下查找用户所关心的主题内容。
2.  快速查阅帮助
    
    在实际应用当中，如果需要快速查阅某项语法时，可以使用关键字进行快速查询。例如，想 知道 show 命令都能看些什么东西，可以用如下命令:
    
        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
        http://dev.mysql.com/doc/refman/5.6/en/extended-show.html.
        
        URL: http://dev.mysql.com/doc/refman/5.6/en/show.html
    
    例如，如果想参看CREATE TABLE 的语法，可以使用以下命令：
    
        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
          | [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}]
              [STORAGE {DISK|MEMORY|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[(fsp)]
          | TIMESTAMP[(fsp)]
          | DATETIME[(fsp)]
          | YEAR
          | CHAR[(length)] [BINARY]
              [CHARACTER SET charset_name] [COLLATE collation_name]
          | VARCHAR(length) [BINARY]
              [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 | SET DEFAULT
        
        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}
          | STATS_AUTO_RECALC [=] {DEFAULT|0|1}
          | STATS_PERSISTENT [=] {DEFAULT|0|1}
          | STATS_SAMPLE_PAGES [=] value
          | TABLESPACE tablespace_name [STORAGE {DISK|MEMORY|DEFAULT}]
          | UNION [=] (tbl_name[,tbl_name]...)
        
        partition_options:
            PARTITION BY
                { [LINEAR] HASH(expr)
                | [LINEAR] KEY [ALGORITHM={1|2}] (column_list)
                | RANGE{(expr) | COLUMNS(column_list)}
                | LIST{(expr) | COLUMNS(column_list)} }
            [PARTITIONS num]
            [SUBPARTITION BY
                { [LINEAR] HASH(expr)
                | [LINEAR] KEY [ALGORITHM={1|2}] (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]
                [TABLESPACE [=] tablespace_name]
                [NODEGROUP [=] node_group_id]
                [(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]
                [TABLESPACE [=] tablespace_name]
                [NODEGROUP [=] node_group_id]
        
        query_expression:
            SELECT ...   (Some valid select or union statement)
        
        CREATE TABLE creates a table with the given name. You must have the
        CREATE privilege for the table.
        
        By default, tables are 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.
        
        For information about the physical representation of a table, see
        http://dev.mysql.com/doc/refman/5.6/en/create-table-files.html.
        
        URL: http://dev.mysql.com/doc/refman/5.6/en/create-table.html
3.  常用的网络资源
    
    [http://dev.mysql.com/downloads/是MySQL][http_dev.mysql.com_downloads_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。
    
    [http://dev.mysql.com/doc/提供了目前最权威的][http_dev.mysql.com_doc] MySQL 数据库及工具的在线手册。
    
    [http://bugs.mysql.com/这里可以查看到MySQL][http_bugs.mysql.com_MySQL] 已经发布的bug 列表，或者向MySQL提交 bug 报告。
    
    [http://www.mysql.com/news-and-events/newsletter/通常会发布各种关于MySQL的最新消息][http_www.mysql.com_news-and-events_newsletter_MySQL]

## 小结： ##

本章简单地介绍了 SQL 语句的基本分类 DML/DDL/DCL，并对每一种分类下的常用 SQL 的用 法进行了举例说明。MySQL 在标准 SQL 的基础上进行了很多扩展，本章对常用的一些语法 做了简单介绍，更详细的说明，读者可以参考 MySQL 的帮助或者官方文档。在本章的最后， 还介绍了用户应如何使用 MySQL 中的帮助文档，以便快速查找各种语法定义

转载于:https://www.cnblogs.com/plf-Jack/p/11117717.html

[http_dev.mysql.com_downloads_MySQL]: http://dev.mysql.com/downloads/%E6%98%AFMySQL
[http_dev.mysql.com_doc]: http://dev.mysql.com/doc/%E6%8F%90%E4%BE%9B%E4%BA%86%E7%9B%AE%E5%89%8D%E6%9C%80%E6%9D%83%E5%A8%81%E7%9A%84
[http_bugs.mysql.com_MySQL]: http://bugs.mysql.com/%E8%BF%99%E9%87%8C%E5%8F%AF%E4%BB%A5%E6%9F%A5%E7%9C%8B%E5%88%B0MySQL
[http_www.mysql.com_news-and-events_newsletter_MySQL]: http://www.mysql.com/news-and-events/newsletter/%E9%80%9A%E5%B8%B8%E4%BC%9A%E5%8F%91%E5%B8%83%E5%90%84%E7%A7%8D%E5%85%B3%E4%BA%8EMySQL%E7%9A%84%E6%9C%80%E6%96%B0%E6%B6%88%E6%81%AF