Demonstration of a MERGE in MySQL that only applies when same PK

mysql_merge_unique_index.sql

CREATE TABLE `sandbox`.`new_table` (
  `id` INT NOT NULL,
  `name` VARCHAR(45) NULL,
  `email` VARCHAR(45) NULL,
  PRIMARY KEY (`id`),
  UNIQUE INDEX `email_UNIQUE` (`email` ASC));

INSERT INTO new_table
(id, name, email)
VALUES
(123, 'John Doe', '[email protected]');

# Different PK, other entity (different identity):
# 0 row(s) affected
INSERT INTO new_table
(id, name, email)
VALUES
(456, 'John Jimmy Doe', '[email protected]')
ON DUPLICATE KEY 
UPDATE name=IF(id != VALUES(id), name, VALUES(name));

# Same PK, same entity (same identity):
# 2 row(s) affected
INSERT INTO new_table
(id, name, email)
VALUES
(123, 'John Jimmy Doe', '[email protected]')
ON DUPLICATE KEY 
UPDATE name=IF(id != VALUES(id), name, VALUES(name));