Ben Chuanlong Du's Blog

It is never too late to learn.

Use Column Alias in SQL

Things on this page are fragmentary and immature notes/thoughts of the author. Please read with your own judgement!

  1. Logically any SELECT is processed in following order:

    1. from
    2. where
    3. group by
    4. having
    5. olap functions
    6. qualify
    7. select
    8. sample
    9. order by

    Besides the proprietary QUALIFY/SAMPLE every DBMS will do it exactly …

Misc Tips on Java

Tips and Traps

  1. Use == (instead of the method Object.equals) to compare objects is a common and tricky mistake for beginner.

  2. You cannot define an abstract static method. This is because "abstract" means that no functionality is implemented while "static" means that functionality exists even there is no object. The two conflict in concept.