How to select the rows affected by an update

When performing an update query (the following is just an example; any update query could be used) such as:

update t1 
inner join t2 on t1.id=t2.id
set t1.name="foo" where t2.name="bar";
Query OK, 324 rows affected (1.82 sec)

how do you see which rows have been affected (the 324 rows affected in the response)? I tried converting the expression to a select, such as

select * from t1 
inner join t2 on t1.id=t2.id
where t1.name="foo";

but this also returns the rows that were already name="foo" before the update, too.
Conceptually, I would like to do something like

select * from rows_affected;

but of course this does not work. Is there a method that will allow the inspection/selection of rows affected by an update query? Or is the only solution to do the select before the update to see which rows will be affected?

This sounds like a job for SELECT FOR UPDATE. Please see MySQL Docs on this

I have discussed this over the years

• Aug 08, 2011 : Are InnoDB Deadlocks exclusive to INSERT/UPDATE/DELETE?

• Jan 02, 2012 : LOCK IN SHARE MODE

• Mar 18, 2012 : select for update gives error on indexed column

• May 09, 2012 : Transaction Lock Timeouts When Updating a Row

• May 13, 2012 : Cannot update certain rows in innodb tables

• Aug 10, 2012 ; Similar function NOWAIT in MySQL

• Feb 12, 2014 : row locking within ACID transaction innodb

StackExchange Database Administrators Q#273636, answer score: 3