¿Corregir MySQL INSERT... EN la sintaxis de CLAVE DUPLICADA?

La sintaxis es la siguiente:

insert into yourTableName values(yourValue1,yourValue2,..N)
on duplicate key update yourColumnName1=yourValue1,yourColumnName2=yourValue2,....N;

Primero creemos una tabla:

mysql> create table DemoTable1539
   -> (
   -> EmployeeName varchar(20),
   -> EmployeeSalary int,
   -> UNIQUE KEY(EmployeeName)
   -> );
Query OK, 0 rows affected (0.62 sec)

Inserte algunos registros en la tabla usando el comando insertar:

mysql> insert into DemoTable1539 values('Chris',4500) on duplicate key update EmployeeName='Robert',EmployeeSalary=8500;
Query OK, 1 row affected (0.20 sec)
mysql> insert into DemoTable1539 values('David',5500) on duplicate key update EmployeeName='Robert',EmployeeSalary=8500;
Query OK, 1 row affected (0.10 sec)
mysql> insert into DemoTable1539 values('Chris',4500) on duplicate key update EmployeeName='Robert',EmployeeSalary=8500;
Query OK, 2 rows affected (0.14 sec)

Muestre todos los registros de la tabla usando la declaración de selección:

mysql> select * from DemoTable1539;

Esto producirá el siguiente resultado:

+--------------+----------------+
| EmployeeName | EmployeeSalary |
+--------------+----------------+
| Robert       |           8500 |
| David        |           5500 |
+--------------+----------------+
2 rows in set (0.00 sec)