HELP

Purpose

Returns search results from the help tables. The search string can contain wildcards such as the percent sign (%) and the underscore (_).

The search string can match one or more topics within a category, or a single topic:

• View the list of top-level help categories:

  HELP 'contents';
  

• View the topics within a help category, for example, search for data types data types:

  HELP 'data_types';
  

• For a specific help topic, you can use one or more associated keywords:

  HELP 'create table'
  

  The returned topics contain the following information:

  • name: the name of the topic.

  • description: the descriptive help text for the topic.

Syntax

HELP 'search_string';

search_string:
   contents | data_types | theme

Parameters

Examples

• View the directory containing all help information.

  obclient> HELP 'contents';
  

  The execution result is as follows:

  You asked for help about help category: "Contents"
  For more information, type 'help <item>', where <item> is one of the following
  categories:
     Data Types
     Functions
     Operator
     Escape character
     Data Definition
     Data Manipulation
     Transaction Statements
     Prepared Statements
     Compound Statements
     Administration
     Utility
  

• View the data types included in the Numeric Type category.

  obclient> HELP 'Numeric Types';
  

  The execution result is as follows:

  You asked for help about help category: "Numeric Types"
  For more information, type 'help <item>', where <item> is one of the following
  topics:
     TINYINT
     BOOL,BOOLEAN
     SMALLINT
     MEDIUMINT
     INT
     INTEGER
     BIGINT
     FLOAT
     DOUBLE
     DOUBLE PRECISION
     FLOAT(p)
     DECIMAL
     NUMERIC
  

• View the usage of the KILL statement.

  obclient> HELP 'KILL';
  

  The execution result is as follows:

  Name: 'KILL'
  Description:
  
    Syntax:
  
    KILL [GLOBAL | LOCAL] [CONNECTION | QUERY] 'sessionid'
  
    Each connection to OceanBase Database runs in an independent thread. You can use the SHOW PROCESSLIST; statement to view the running threads and use the KILL thread_id statement to terminate a thread.
  
  • KILL CONNECTION is the same as KILL without modifiers: it terminates the thread with the given thread_id.
  
  • KILL QUERY terminates the statement currently being executed by the connection, but keeps the connection open.
  If you have the PROCESS privilege, you can view all threads. If you have the SUPER privilege, you can terminate all threads and statements. Otherwise, you can only view and terminate your own threads and statements.
  

• View the syntax of the SELECT statement.

  obclient> HELP SELECT;
  

  The execution result is as follows:

  Name: 'SELECT'
  Description:
  
    This statement is used to query the contents of a table.
  
    Basic query
  
    Syntax:
  
    SELECT
      [ALL | DISTINCT]
        selectexpr [AS othername] [, selectexpr ...]
        [FROM table_references]
          [WHERE where_conditions]
      [GROUP BY group_by_list]
      [HAVING search_confitions]
      [ORDER BY order_list]
      [LIMIT {[offset,] rowcount | rowcount OFFSET offset}]
          [FOR UPDATE];