Sql

/* 
references:
- https://dev.mysql.com/doc/refman/5.7/en/insert-on-duplicate.html
- https://stackoverflow.com/questions/32777081/bulk-insert-and-update-in-mysql
- https://thewebfellas.com/blog/conditional-duplicate-key-updates-with-mysql
*/

/* create a new database and use it */
drop database if exists test_upsert;
create database test_upsert;
use test_upsert;

/* create the upsert table for testing */
drop table if exists upsert_table;
create table upsert_table 
(
	id int(11) unsigned not null primary key auto_increment,
	unkey1 varchar(10) not null, 
	unkey2 varchar(10) not null, 
	val1 varchar(100) not null, 
	val2 varchar(100) not null, 
	lastmodified int(11) unsigned,
	unique(unkey1, unkey2)
) engine=innodb default charset=utf8mb4;

/* perform the initial vanilla bulk data load */
insert into upsert_table 
	(unkey1, unkey2, val1, val2, lastmodified)
values
	('A', '11', 'Meeting A', 'room 1-1', UNIX_TIMESTAMP('2017-08-25 20:00:01')),
	('B', '22', 'Meeting B', 'room 2-2', UNIX_TIMESTAMP('2017-08-25 20:00:02')),
	('C', '33', 'Meeting C', 'room 3-3', UNIX_TIMESTAMP('2017-08-25 20:00:03')),
	('D', '44', 'Meeting D', 'room 4-4', UNIX_TIMESTAMP('2017-08-25 20:00:04')),
	('E', '55', 'Meeting E', 'room 5-5', UNIX_TIMESTAMP('2017-08-25 20:00:05'));

/* view the inserted data */
select * from upsert_table;
/*
+----+--------+--------+-----------+----------+--------------+
| id | unkey1 | unkey2 | val1      | val2     | lastmodified |
+----+--------+--------+-----------+----------+--------------+
|  1 | A      | 11     | Meeting A | room 1-1 |   1503662401 |
|  2 | B      | 22     | Meeting B | room 2-2 |   1503662402 |
|  3 | C      | 33     | Meeting C | room 3-3 |   1503662403 |
|  4 | D      | 44     | Meeting D | room 4-4 |   1503662404 |
|  5 | E      | 55     | Meeting E | room 5-5 |   1503662405 |
+----+--------+--------+-----------+----------+--------------+
*/

/* the actual upsert + "conditional" data update based on timestamp */
insert into upsert_table 
	(unkey1, unkey2, val1, val2, lastmodified)
values
	('A', '11', 'Updated Meeting A', 'room 1-10', UNIX_TIMESTAMP('2017-08-25 20:00:11')),
	('B', '22', 'Should not update Meeting B', 'room 2-20', UNIX_TIMESTAMP('2017-08-25 19:00:02')),
	('F', '66', 'New Meeting F', 'room 6-6', UNIX_TIMESTAMP('2017-08-25 20:00:06'))
on duplicate key update
	val1 = if (lastmodified < values(lastmodified), values(val1), val1),
	val2 = if (lastmodified < values(lastmodified), values(val2), val2),
	lastmodified = if (lastmodified < values(lastmodified), values(lastmodified), lastmodified);

/* 
verify that 
row with key "A"-"11" should be updated because data with same unique key exists and timestamp is greater than existing timestamp
row with key "B"-"22" should not be updated although data with same unique key exists because the timestamp is lesser than existing timestamp (actually updated with the existing value) 
row with key "F"-"66" should be inserted because data with same unique key does not exist
*/	
select * from upsert_table;
/*
+----+--------+--------+-------------------+-----------+--------------+
| id | unkey1 | unkey2 | val1              | val2      | lastmodified |
+----+--------+--------+-------------------+-----------+--------------+
|  1 | A      | 11     | Updated Meeting A | room 1-10 |   1503662411 |
|  2 | B      | 22     | Meeting B         | room 2-2  |   1503662402 |
|  3 | C      | 33     | Meeting C         | room 3-3  |   1503662403 |
|  4 | D      | 44     | Meeting D         | room 4-4  |   1503662404 |
|  5 | E      | 55     | Meeting E         | room 5-5  |   1503662405 |
|  6 | F      | 66     | New Meeting F     | room 6-6  |   1503662406 |
+----+--------+--------+-------------------+-----------+--------------+
*/