MySQL :: MySQL 8.4 Reference Manual :: 15.8.3 HELP Statement (original) (raw)

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 (seeSection 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 theLIKE 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 asData Types, use the category name:

HELP 'data types'  

• For help on a specific help topic, such as theASCII() function or theCREATE 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/8.4/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 BINARY LOG STATUS  
   SHOW ENGINE  
   SHOW FUNCTION STATUS  
   SHOW PROCEDURE STATUS  
   SHOW REPLICA 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