The statement above sets the value of the c1 to its current value specified by the expression values(c1) plus 1 if there is a duplicate in unique index or primary key. mysql insert on duplicate key update example. let’s take a look at an example of using the insert on duplicate key update to understand how it works.. 13.2.5.3 insert on duplicate key update syntax. if you specify on duplicate key update, and a row is inserted that would cause a duplicate value in a unique index or primary key, mysql performs an update of the old row.. 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..
