find the 2nd highest salary of an emplyee code example

Example 1: sql select second max

Both options you find max as a subset and then exclude from main select
sql> SELECT MAX( col ) FROM table
 	WHERE col < ( SELECT MAX( col ) FROM table);
sql> SELECT MAX(col) FROM table 
WHERE col NOT IN (SELECT MAX(col) FROM table);

Example 2: second max salary in sql

SELECT MAX(SALARY) 'SECOND_MAX' FROM EMPLOYEES
WHERE SALARY <> (SELECT MAX(SALARY) FROM EMPLOYEES);