I have never heard of UPDATE INNER JOIN before, and I suspect that is
an extension that is unique to MS Access.
The [latest release][1] of SQLite adds support for [UPDATE FROM][2].
This is also a non-standard SQL extension, but in the case of SQLite,
we attempted to copy the syntax of [PostgreSQL][3] as closely as we
could. I suspect that you will want to translate your query into
a suitable UPDATE FROM statement.
[1]: https://www.sqlite.org/releaselog/3_33_0.html
[2]: https://www.sqlite.org/lang_update.html#upfrom
[3]: https://www.postgresql.org/docs/9.1/sql-update.html
The offical way to quote identifiers in SQL is double quotes:
~~~~
UPDATE "activity_overview" ....
~~~~
The use of `[...]` for identifier quoting is distinctive to SQL Server and
MS-Access. SQLite tries to copy that for compatibility. But you really
should get into the habit of using the SQL standard `"..."` quoting if you can.