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MySQL 8.0 Reference Manual  /  ...  /  HELP Statement

15.8.3 HELP Statement

HELP 'search_string'

The HELP statement returns online information from the MySQL Reference Manual. Its proper operation requires that the help tables in the mysql database be initialized with help topic information (see Section 7.1.17, “Server-Side Help Support”).

The HELP statement searches the help tables for the given search string and displays the result of the search. The search string is not case-sensitive.

The search string can contain the wildcard characters % and _. These have the same meaning as for pattern-matching operations performed with the LIKE operator. For example, HELP 'rep%' returns a list of topics that begin with rep.

The HELP statement does not require a terminator such as ; or \G.

The HELP statement understands several types of search strings:

  • At the most general level, use contents to retrieve a list of the top-level help categories:

    HELP 'contents'
  • For a list of topics in a given help category, such as Data Types, use the category name:

    HELP 'data types'
  • For help on a specific help topic, such as the ASCII() function or the CREATE TABLE statement, use the associated keyword or keywords:

    HELP 'ascii'
    HELP 'create table'

In other words, the search string matches a category, many topics, or a single topic. The following descriptions indicate the forms that the result set can take.

  • Empty result

    No match could be found for the search string.

    Example: HELP 'fake'

    Yields:

    Nothing found
    Please try to run 'help contents' for a list of all accessible topics
  • Result set containing a single row

    This means that the search string yielded a hit for the help topic. The result includes the following items:

    • name: The topic name.

    • description: Descriptive help text for the topic.

    • example: One or more usage examples. (May be empty.)

    Example: HELP 'log'

    Yields:

    Name: 'LOG'
    Description:
    Syntax:
    LOG(X), LOG(B,X)
    
    If called with one parameter, this function returns the natural
    logarithm of X. If X is less than or equal to 0.0E0, the function
    returns NULL and a warning "Invalid argument for logarithm" is
    reported. Returns NULL if X or B is NULL.
    
    The inverse of this function (when called with a single argument) is
    the EXP() function.
    
    URL: https://dev.mysql.com/doc/refman/8.0/en/mathematical-functions.html
    
    Examples:
    mysql> SELECT LOG(2);
            -> 0.69314718055995
    mysql> SELECT LOG(-2);
            -> NULL
  • List of topics.

    This means that the search string matched multiple help topics.

    Example: HELP 'status'

    Yields:

    Many help items for your request exist.
    To make a more specific request, please type 'help <item>',
    where <item> is one of the following topics:
       FLUSH
       SHOW
       SHOW ENGINE
       SHOW FUNCTION STATUS
       SHOW MASTER STATUS
       SHOW PROCEDURE STATUS
       SHOW REPLICA STATUS
       SHOW SLAVE STATUS
       SHOW STATUS
       SHOW TABLE STATUS
  • List of topics.

    A list is also displayed if the search string matches a category.

    Example: HELP 'functions'

    Yields:

    You asked for help about help category: "Functions"
    For more information, type 'help <item>', where <item> is one of the following
    categories:
       Aggregate Functions and Modifiers
       Bit Functions
       Cast Functions and Operators
       Comparison Operators
       Date and Time Functions
       Encryption Functions
       Enterprise Encryption Functions
       Flow Control Functions
       GROUP BY Functions and Modifiers
       GTID
       Information Functions
       Internal Functions
       Locking Functions
       Logical Operators
       Miscellaneous Functions
       Numeric Functions
       Performance Schema Functions
       Spatial Functions
       String Functions
       Window Functions
       XML