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mysqlAtomic select and update (e.g. fetch unique rows on each request)


START TRANSACTION;
SELECT id FROM tbl WHERE processed = 0 LIMIT 1 FOR UPDATE;
UPDATE tbl SET processed = 1 WHERE id = 2;
COMMIT;ctrl + c
START TRANSACTION

starts transaction

tbl

table to select rows from

processed = 0

condition to select rows from table

LIMIT 1

select only one row

FOR UPDATE

lock selected rows till they are updated by us

SET processed = 1

updated selected row (after possible processing)

id = 2

condition to update selected row (use fetched ID of a row)

COMMIT

finish transaction (lock will be released after that)