Getting help

isql comes with the HELP command. This gives brief details of most of the commands available - unfortunately, some are missing. The HELP command also allows you to drill down for further information. To activate the help system, simply type HELP at the prompt, as shown below (from Firebird 2.5):

SQL> help; 

Frontend commands:
BLOBDUMP <blobid> <file>         -- dump BLOB to a file
BLOBVIEW <blobid>                -- view BLOB in text editor
EDIT        [<filename>]         -- edit SQL script file and execute
EDIT                             -- edit current command buffer and execute
HELP                             -- display this menu
INput        <filename>          -- take input from the named SQL file
OUTput      [<filename>]         -- write output to named file
OUTput                           -- return output to stdout
SET          <option>            -- (Use HELP SET for complete list)
SHELL        <command>           -- execute Operating System command in sub-shell
SHOW         <object> [<name>]   -- display system information
             <object> =           CHECK, COLLATION, DATABASE, DOMAIN, EXCEPTION, FILTER, FUNCTION, 
                                  GENERATOR, GRANT, INDEX, PROCEDURE, ROLE, SQL DIALECT, SYSTEM,
                                  TABLE, TRIGGER, VERSION, USERS, VIEW
EXIT                             -- exit and commit changes
QUIT                             -- exit and roll back changes

All commands may be abbreviated to letters in CAPitals

Most of these commands have no further levels of detail, while the SET command does. To drill down into those extra levels, proceed as follows:

SQL> help set;

Set commands:
    SET                          -- display current SET options
    SET AUTOddl                  -- toggle autocommit of DDL statements
    SET BAIL                     -- toggle bailing out on errors in non-interactive mode
    SET BLOB [ALL|<n>]           -- display BLOBS of subtype <n> or ALL
    SET BLOB                     -- turn off BLOB display
    SET COUNT                    -- toggle count of selected rows on/off
    SET ROWCOUNT [<n>]           -- limit select stmt to <n> rows, zero is no limit
    SET ECHO                     -- toggle command echo on/off
    SET HEADING                  -- toggle display of query column titles
    SET LIST                     -- toggle column or table display format
    SET NAMES <csname>           -- set name of runtime character set
    SET PLAN                     -- toggle display of query access plan
    SET PLANONLY                 -- toggle display of query plan without executing
    SET SQL DIALECT <n>          -- set sql dialect to <n>
    SET STATs                    -- toggle display of performance statistics
    SET TIME                     -- toggle display of timestamp with DATE values
    SET TERM <string>            -- change statement terminator string
    SET WIDTH <col> [<n>]        -- set/unset print width to <n> for column <col>

All commands may be abbreviated to letters in CAPitals

If you attempt to drill down into any other command, the effect is exactly the same as executing the HELP command on its own.

Note: In the output from HELP SET, there doesn't appear to be any help on the SET TRANSACTION command.