Syntax
------

INSERT [LOW_PRIORITY | DELAYED | HIGH_PRIORITY] [IGNORE]
 [INTO] tbl_name [PARTITION (partition_list)] [(col,...)]
 {VALUES | VALUE} ({expr | DEFAULT},...),(...),...
 [ ON DUPLICATE KEY UPDATE
  col=expr
   [, col=expr] ... ]

Or:

INSERT [LOW_PRIORITY | DELAYED | HIGH_PRIORITY] [IGNORE]
  [INTO] tbl_name [PARTITION (partition_list)]
  SET col={expr | DEFAULT}, ...
  [ ON DUPLICATE KEY UPDATE
   col=expr
    [, col=expr] ... ]

Or:

INSERT [LOW_PRIORITY | HIGH_PRIORITY] [IGNORE]
  [INTO] tbl_name [PARTITION (partition_list)] [(col,...)]
  SELECT ...
  [ ON DUPLICATE KEY UPDATE
   col=expr
    [, col=expr] ... ]

Description
-----------

INSERT ... ON DUPLICATE KEY UPDATE is a MariaDB/MySQL extension to the INSERT
statement that, if it finds a duplicate unique or primary key, will instead
perform an UPDATE.

The row/s affected value is reported as 1 if a row is inserted, and 2 if a row
is updated, unless the API's CLIENT_FOUND_ROWS flag is set.

If more than one unique index is matched, only the first is updated. It is not
recommended to use this statement on tables with more than one unique index.

If the table has an AUTO_INCREMENT primary key and the statement inserts or
updates a row, the LAST_INSERT_ID() function returns its AUTO_INCREMENT value.

The VALUES() function can only be used in a ON DUPLICATE KEY UPDATE clause and
has no meaning in any other context. It returns the column values from the
INSERT portion of the statement. This function is particularly useful for
multi-rows inserts.

The IGNORE and DELAYED options are ignored when you use ON DUPLICATE KEY
UPDATE.

See Partition Pruning and Selection for details on the PARTITION clause.

This statement activates INSERT and UPDATE triggers. See Trigger Overview for
details.

See also a similar statement, REPLACE.

Examples
--------

CREATE TABLE ins_duplicate (id INT PRIMARY KEY, animal VARCHAR(30));
INSERT INTO ins_duplicate VALUES (1,'Aardvark'), (2,'Cheetah'), (3,'Zebra');

If there is no existing key, the statement runs as a regular INSERT:

INSERT INTO ins_duplicate VALUES (4,'Gorilla') 
 ON DUPLICATE KEY UPDATE animal='Gorilla';
Query OK, 1 row affected (0.07 sec)

SELECT * FROM ins_duplicate;
+----+----------+
| id | animal   |
+----+----------+
|  1 | Aardvark |
|  2 | Cheetah  |
|  3 | Zebra    |
|  4 | Gorilla  |
+----+----------+

A regular INSERT with a primary key value of 1 will fail, due to the existing
key:

INSERT INTO ins_duplicate VALUES (1,'Antelope');
ERROR 1062 (23000): Duplicate entry '1' for key 'PRIMARY'

However, we can use an INSERT ON DUPLICATE KEY UPDATE instead:

INSERT INTO ins_duplicate VALUES (1,'Antelope') 
 ON DUPLICATE KEY UPDATE animal='Antelope';
Query OK, 2 rows affected (0.09 sec)

Note that there are two rows reported as affected, but this refers only to the
UPDATE.

SELECT * FROM ins_duplicate;
+----+----------+
| id | animal   |
+----+----------+
|  1 | Antelope |
|  2 | Cheetah  |
|  3 | Zebra    |
|  4 | Gorilla  |
+----+----------+

Adding a second unique column:

ALTER TABLE ins_duplicate ADD id2 INT;
UPDATE ins_duplicate SET id2=id+10;
ALTER TABLE ins_duplicate ADD UNIQUE KEY(id2);

Where two rows match the unique keys match, only the first is updated. This
can be unsafe and is not recommended unless you are certain what you are doing.

INSERT INTO ins_duplicate VALUES (2,'Lion',13) 
 ON DUPLICATE KEY UPDATE animal='Lion';
Query OK, 2 rows affected (0.004 sec)

SELECT * FROM ins_duplicate;
+----+----------+------+
| id | animal   | id2  |
+----+----------+------+
|  1 | Antelope |   11 |
|  2 | Lion     |   12 |
|  3 | Zebra    |   13 |
|  4 | Gorilla  |   14 |
+----+----------+------+

Although the third row with an id of 3 has an id2 of 13, which also matched,
it was not updated.

Changing id to an auto_increment field. If a new row is added, the
auto_increment is moved forward. If the row is updated, it remains the same.

ALTER TABLE `ins_duplicate` CHANGE `id` `id` INT( 11 ) NOT NULL AUTO_INCREMENT;
ALTER TABLE ins_duplicate DROP id2;
SELECT Auto_increment FROM INFORMATION_SCHEMA.TABLES 
 WHERE TABLE_NAME='ins_duplicate';
+----------------+
| Auto_increment |
+----------------+
|              5 |
+----------------+

INSERT INTO ins_duplicate VALUES (2,'Leopard') 
 ON DUPLICATE KEY UPDATE animal='Leopard';
Query OK, 2 rows affected (0.00 sec)

SELECT Auto_increment FROM INFORMATION_SCHEMA.TABLES 
 WHERE TABLE_NAME='ins_duplicate';
+----------------+
| Auto_increment |
+----------------+
|              5 |
+----------------+

INSERT INTO ins_duplicate VALUES (5,'Wild Dog') 
 ON DUPLICATE KEY UPDATE animal='Wild Dog';
Query OK, 1 row affected (0.09 sec)

SELECT * FROM ins_duplicate;
+----+----------+
| id | animal   |
+----+----------+
|  1 | Antelope |
|  2 | Leopard  |
|  3 | Zebra    |
|  4 | Gorilla  |
|  5 | Wild Dog |
+----+----------+

SELECT Auto_increment FROM INFORMATION_SCHEMA.TABLES 
 WHERE TABLE_NAME='ins_duplicate';
+----------------+
| Auto_increment |
+----------------+
|              6 |
+----------------+

Refering to column values from the INSERT portion of the statement:

INSERT INTO table (a,b,c) VALUES (1,2,3),(4,5,6)
  ON DUPLICATE KEY UPDATE c=VALUES(a)+VALUES(b);

See the VALUES() function for more.

URL: https://mariadb.com/kb/en/insert-on-duplicate-key-update/