Order of execution of apex code

Order of execution of apex code:

1. Before triggers:

     If we update child records in before triggers then parent record automatically update.

2. Validation rules:

 If validation matches the criteria then error will populate in same page.

Runs most system validation steps again, such as verifying that all required fields have a non-null value, and runs any user-defined validation rules. The only system validation that Salesforce does not run a second time (when the request comes from a standard UI edit page) is the enforcement of layout-specific rules.

*Note: Saves the record to the database, but does not commit yet.

3. After Triggers:

4. Assignment Rules:

5. Auto Response Rules:

6. Workflow Rules:

If there are workflow field updates, updates the record again.

7. Escalation Rules:

       If the record contains a roll-up summary field or is part of a cross-object workflow, performs calculations and updates the roll-up summary field in the parent record. Parent record goes through save procedure.

     If the parent record is updated, and a grand-parent record contains a roll-up summary field or is part of a cross-object workflow, performs calculations and updates the roll-up summary field in the parent record. Grand-parent record goes through save procedure.

Executes Criteria Based Sharing evaluation.

Commits all DML operations to the database.

Executes post-commit logic, such as sending emails