The conditional-or operator is syntactically left-associative (it groups left-to-right).
At run-time, the left-hand operand expression is evaluated first; if the result has type Boolean, it is subjected to unboxing conversion (§5.1.8).
If the resulting value is true, the value of the conditional-or expression is true and the right-hand operand expression is not evaluated.
START TRANSACTION;
UPDATE mytable SET is_deleted=1;
INSERT INTO mytable (field1, field2, ...) VALUES
('field1', 'field2', ...), ('field1', 'field2', ...), ('field1', 'field2', ...), ...
ON DUPLICATE KEY UPDATE
is_deleted=0,
field1=VALUES(field1),
field2=VALUES(field2),
...
;
COMMIT;
