How to UPDATE in SQLite using a LEFT JOIN to select candidate rows

Question

I have a table assoc containing columns

local_id, remote_id, cachedData

I can successfully run an SQLITE query that looks like

Answer 1

If assoc has a single column as the primary key (and assuming that it is local_id):

UPDATE assoc
SET cachedData=NULL
WHERE local_id IN (
  SELECT local_id FROM assoc a1 LEFT JOIN ...
);

Answer 2

 UPDATE assoc SET cachedData = NULL
    WHERE EXISTS (SELECT * FROM otherTable 
        WHERE otherTable.Col1 = assoc.Col1 AND otherTable.Col2 = assoc.Col1)

Be aware that this is not especially performant.

Answer 3

Aha, there's already a builtin rowid!

UPDATE assoc
SET cachedData=NULL
WHERE rowid IN (
   SELECT rowid FROM assoc a1 LEFT JOIN ...
);