db2数据库There is no physical unique key defined. You can define a custom unique key

in DB2 database, you can define a custom unique key by using the CREATE UNIQUE INDEX statement. This statement allows you to specify one or more columns as the key and ensures that the values in those columns are unique for each row in the table.

For example, to create a unique key on the "employee_id" column in the "employees" table, you can use the following SQL statement:

CREATE UNIQUE INDEX emp_id_unique ON employees(employee_id);

This will create a unique index called "emp_id_unique" on the "employee_id" column, which will prevent duplicate values from being inserted into the table.