SQL Statement Execution Flow

Suppose we have a following SQL statement.

select  employee_id, first_name

from hr.employees

where employee_id = 120

order by first_name

This statement will be validated in the following order

• Table list in the FROM clause
• Order BY clause columns, expressions
• Where clause conditions
• Finally Select list

Similarly for the following SQL

select employee_id, first_name, sum(salary)

 from hr.emp_data

where salary <> 0

group by employee_id, first_name

having sum(salary) > 0

order by employee_id, first_name

• Table list in the FROM clause
• Order BY clause columns, expressions
• Having Clause
• Group By Clause
• Where clause conditions
• Finally Select list