I have implemented a similar feature based on Perconar server 5.5.18, the syntax is:
SELECT
select_expr [, select_expr ...]
FROM UPDATE
[LOW_PRIORITY] [IGNORE]
[TARGET_AFFECT_ROW num]
tbl_name
SET col_name1=
[, col_name2=
{expr2|DEFAULT}] ... [WHERE where_condition] [ORDER BY ...] [LIMIT row_count]
for short: SELECT...FROM UPDATE...
I know that Oracle and PostgreSQL use the RETURNING syntax, but for MySQL(Oracle/Percona version) that requires JDBC to make some changes, which will
cause compatibility problems
more detail about "SELECT...FROM...UPDATE", please refer to: https://bugs.launchpad.net/percona-server/+bug/1311471
Hi akhilseshan yes, every task labeled as gsoc18 is available. Feel free to ask any questions you have in this issue tracker and submit your proposal with an implementation plan for it.
hi Igor Babaev
I'm Rajiv Nayan, a third year undergraduate in Computer science at AIETM college Jaipur , India. I would like do this project for GSoC 2018. It would be greatly appreciated if you could help me get started.
hello i am sahaj jain from Delhi Technological University, I am familiar with the topics associated with this project and would be happy to take it as my gsoc project. Mentors can mail me at ssaahhaajj@gmail.com to discuss details as i cant find yours here 
Hi Rajiv,
You probably meant GSoC 2019
Anyway first of all I need your email address.
ssaahhaajj We encourage students to email questions to the dev mailing list.
I suggest you fire and email to maria-developers mailing list.
https://launchpad.net/~maria-developers
With all your questions. That way the answers are available for everyone. Alternatively, you can post your questions on the JIRA task too, but the developers mailing list has more eyes watching it.
Ali patch: https://github.com/alibaba/AliSQL/commit/4f246a8450bbf832178abff80e0fbcafd4068b71
In addition to the proposed implementation to return new values, I would also like this to include the ability to return the old values as well. Something like:
UPDATE table SET col1 = val1 RETURNING old.col1 AS oldCol1Val, new.col1 as newCol1Val;
+1 for NEW.col and OLD.col.
But then, notice that this should also be added to INSERT ON DUPLICATE KEY UPDATE and REPLACE, both for consistency and because it's useful.