Short answer: use `(SELECT * FROM myTable) AS something`

The problem is that MySQL, for whatever inane reason, doesn't allow you to write queries like this:

UPDATE myTable

SET myTable.A =

(

SELECT B

FROM myTable

INNER JOIN ...

)

That is, if you're doing an UPDATE/INSERT/DELETE on a table, you can't reference that table in an inner query (you can however reference a field from that outer table...)

The solution is to replace the instance of myTable in the sub-query with (SELECT * FROM myTable), like this:

UPDATE myTable

SET myTable.A =

(

SELECT B

FROM (SELECT * FROM myTable) AS something

INNER JOIN ...

)

This apparently causes the necessary fields to be implicitly copied into a temporary table, so it's allowed