The "sqlite3" command:

Usage: fossil sql ?OPTIONS?

Run the standalone sqlite3 command-line shell on DATABASE with SHELL_OPTS.
If DATABASE is omitted, then the repository that serves the working
directory is opened.  See https://www.sqlite.org/cli.html for additional
information.

Options:

   --no-repository           Skip opening the repository database.

   -R REPOSITORY             Use REPOSITORY as the repository database

WARNING:  Careless use of this command can corrupt a Fossil repository
in ways that are unrecoverable.  Be sure you know what you are doing before
running any SQL commands that modify the repository database.

The following extensions to the usual SQLite commands are provided:

   checkin_mtime(X,Y)        Return the mtime for the file Y (a BLOB.RID)
                             found in check-in X (another BLOB.RID value).

   compress(X)               Compress text X.

   content(X)                Return the content of artifact X. X can be an
                             artifact hash or hash prefix or a tag. Artifacts
                             are stored compressed and deltaed. This function
                             does all necessary decompression and undeltaing.

   decompress(X)             Decompress text X.  Undoes the work of
                             compress(X).

   delta_apply(X,D)          Apply delta D to source blob X and return
                             the result.

   delta_create(X,Y)         Create and return a delta that will convert
                             X into Y.

   delta_output_size(D)      Return the number of bytes of output to expect
                             when applying delta D

   delta_parse(D)            A table-valued function that deconstructs
                             delta D and returns rows for each element of
                             that delta.

   files_of_checkin(X)       A table-valued function that returns info on
                             all files contained in check-in X.  Example:
                               SELECT * FROM files_of_checkin('trunk');

   now()                     Return the number of seconds since 1970.

   REGEXP                    The REGEXP operator works, unlike in
                             standard SQLite.

   symbolic_name_to_rid(X)   Return the BLOB.RID corresponding to symbolic
                             name X.