Essays, poems, and personal reflections from the desk and drawer.

essay

macOS and iOS 26 public beta impressions

26 July 2025

I installed macOS and iOS 26 public beta today. The main attraction in this update is the design change called Liquid Glass...

essay

Useful PL/SQL queries

20 July 2025

In this post, I’m sharing some handy PL/SQL queries that help with monitoring and maintaining Oracle databases...

notes

NOT IN vs NOT EXISTS in PL/SQL

19 June 2025

SELECT *
FROM TABLE1 
WHERE ID NOT IN (
    SELECT ID
    FROM TABLE2
)

When I ran the above query I know the condition will give me the results, because the data exists in the TABLE1 which is not in TABLE2. But I didn’t go any results. I got surprised. After I a while I found out the issue.

So the reason is that ID column in the TABLE2 have null values. If any value of ID in the subquery is NULL, then the entire NOT IN clause fails to match anything. This is standard SQL behavior because NULL makes the whole comparison unknown.

Solution:

  1. You can use NOT NULL condition in the sub-query as below:
SELECT *
FROM TABLE1 
WHERE ID NOT IN (
    SELECT ID
    FROM TABLE2
    WHERE ID IS NOT NULL
)
  1. Use NOT EXISTS:
SELECT *
FROM TABLE1 T1
WHERE NOT EXISTS (
    SELECT 1
    FROM TABLE2 T2
    WHERE T1.ID = T2.ID
)

The NOT EXISTS will automatically handle null values and safer to use.

References

StackOverflow, Geeks for geeks

essay

Difference between React and ReactDOM

13 June 2025

React is a JavaScript library for building user interfaces. ReactDOM, on the other hand, is a library that provides an interface between React and the DOM...

notes

Unhang Windows PC

26 May 2025

I often found that Ctrl+Alt+Delete unhangs the Windows PC. I googled why?

The nutshell answer is : Ctrl+Alt+Delete is a secure attention sequence (SAS) triggers a system interrupt, effectively forcing the computer to respond. This is directly handled by the Windows operating system kernel. That means it can bypass most of the stuff that’s currently running (including frozen apps or even some parts of the graphical interface).

Cool to know this.

essay

Featured posts in Hugo

24 May 2025

Today, I updated the about page to display featured blog sections dynamically using front matter tags. This replaces the previous hardcoded method for a more flexible setup.

notes

Diffdiff and Emoji Kitchen

19 May 2025

I just found two tools:

Thunder and Unicorn mixed by Emoji Kitchen

notes

Google AI Overview

18 May 2025

I don’t search for things as much as I used to. These days, I just go straight to ChatGPT. I don’t feel like Googling and clicking through multiple pages to find the best answer. I ask ChatGPT, and most of the time, the results are satisfying.

I’ve heard that traditional Google searches are declining. But now, they’ve introduced AI Overviews at the top of their results. I think it’s a good idea—because we get a quick summary of what we’re looking for, along with links to other websites. Yes, I think it’s a good move.

Google AI Overview for my theme Lightbi

notes

Custom folder Icons with Material Icon Theme

12 May 2025

Install Material Icon Theme

In settings.json:

"material-icon-theme.folders.associations": {
  "folder-name": "Home"
}

folder-name is the folder name and Home is the icon. You can find the files and folders icons in here.