In-depth analysis of MySQL "On duplicate key update" syntax

If an on duplicate key update is specified at the end of the INSERT statement, and the row is inserted to cause duplicate values in a unique index or primary key, update is performed on the row where the duplicate value occurs, and if the unique value column is not duplicated. The new row is inserted.
For example, if column A is a primary key or has a unique index and contains a value of 1, the following two statements have the same effect:   

INSERT  into TABLE(A,C)VALUES(1,3) onDUPLICATEKEY UPDATEC=C+1;UPDATE TABLE SETC=C+1 WHEREA=1;

　　Note: On DUPLICATE KEY update is only a unique syntax for MySQL, not SQL standard syntax!
This syntax and suitability is used in scenarios where it is necessary to determine whether a record exists or not, and the insertion exists.

In-depth analysis of MySQL "On duplicate key update" syntax