Essays

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Notes

In Oracle PL/SQL, you can use the following commands to view table details:

1. DESCRIBE or DESC

   DESC table_name;
   

   Displays columns, data types, and constraints.

2. USER_TAB_COLUMNS

   SELECT COLUMN_NAME, DATA_TYPE, DATA_LENGTH
   FROM USER_TAB_COLUMNS
   WHERE TABLE_NAME = 'TABLE_NAME';
   

   Shows details about columns for tables owned by the user.

3. ALL_TAB_COLUMNS

   SELECT COLUMN_NAME, DATA_TYPE, DATA_LENGTH
   FROM ALL_TAB_COLUMNS
   WHERE TABLE_NAME = 'TABLE_NAME';
   

   Provides column information for tables accessible to the user.

4. DBMS_METADATA.GET_DDL

   SELECT DBMS_METADATA.GET_DDL('TABLE', 'TABLE_NAME') FROM DUAL;
   

   Displays the CREATE TABLE statement for table structure details.

To view constraints on the table, you can check here.

If your Oracle database has Flashback enabled, you can query past versions of data within a specified retention period. Here’s how to use Flashback to retrieve a prior state of data:

SELECT * 
FROM your_table AS OF TIMESTAMP (SYSTIMESTAMP - INTERVAL '5' MINUTE) 
WHERE your_condition;

Replace SYSTIMESTAMP - INTERVAL '5' MINUTE with the timestamp or interval that reflects when the data was last known to be in its old state.

Note: Flashback must be enabled, and it’s only available within the Flashback retention window, which depends on your database configuration.

Breaking columns to a new line in flexbox requires a small hack: add an element with width: 100% wherever you want to wrap your columns to a new line.

<div class="container text-center">
  <div class="row">
    <div class="col-6 col-sm-3">.col-6 .col-sm-3</div>
    <div class="col-6 col-sm-3">.col-6 .col-sm-3</div>

    <!-- Force next columns to break to new line -->
    <div class="w-100"></div>

    <div class="col-6 col-sm-3">.col-6 .col-sm-3</div>
    <div class="col-6 col-sm-3">.col-6 .col-sm-3</div>
  </div>
</div>

You can also apply this break at specific breakpoints with our responsive display utilities.

<div class="container text-center">
  <div class="row">
    <div class="col-6 col-sm-4">.col-6 .col-sm-4</div>
    <div class="col-6 col-sm-4">.col-6 .col-sm-4</div>

    <!-- Force next columns to break to new line at md breakpoint and up -->
    <div class="w-100 d-none d-md-block"></div>

    <div class="col-6 col-sm-4">.col-6 .col-sm-4</div>
    <div class="col-6 col-sm-4">.col-6 .col-sm-4</div>
  </div>
</div>

References

Bootstrap Doc

To update a column with a random value in PL/SQL, you can use the DBMS_RANDOM package, which provides functions for generating random numbers or strings.

To update random number

BEGIN
    UPDATE employees
    SET salary = ROUND(DBMS_RANDOM.VALUE(100, 500));
    COMMIT;
END;

• DBMS_RANDOM.VALUE(100, 500) generates a random decimal number between 100 and 500.
• ROUND is used to convert the decimal value to an integer.

To update random string

BEGIN
   UPDATE employees
    SET password = DBMS_RANDOM.STRING('x', 8);  -- 'x' specifies alphanumeric characters
    COMMIT;
END;

• DBMS_RANDOM.STRING('x', 8) generates an 8-character alphanumeric string.
• ‘x’ specifies alphanumeric characters (letters and numbers). Other options include ‘a’ for alphabets and ‘u’ for uppercase only.

The PL/SQL MINUS operator returns all rows from the first query that are not present in the second query. Each SELECT statement defines a dataset, and the MINUS operator retrieves all records from the first dataset, excluding any that also appear in the second dataset.

select stock_id, stock_name
from stock_master
where active = 'Y'

minus

select stock_poid, stock_desc
from stock_ledger
where transaction_date > '01-JAN-24'

References

Tech on the net

In Hugo, creating different slash pages (like /about/, /uses/, etc.) involves creating specific content files for each page and customizing templates as needed.

• Create individual markdown files for each slash page under content/.
  If you want to create an /about/ page in your blog, add a markdown page with below front matter in the content/ page.

//content/about.md

---
title: "About"
date: 2024-10-16
---

This is the About page content.

• Optionally create a template for the page.
  Hugo uses the single.html template from the layouts/_default/ folder to render pages by default. However, you can create custom templates in the layouts/page/ folder to format specific pages as needed.

//layouts/page/about.html

<h1>{{ .Title }}</h1>
<div class="content">
  {{ .Content }}
</div>

You can check my slash pages like uses, credits, and changelog.

References

Hugo Docs

Hugo is fast, but ineffecinet templates can make it slower. For checking the performance you can use the below commands.

• Use hugo --logLevel debug to display debug information, warning, and error message.

• Use hugo --templateMetrics to check for slow templates. This will show the time it takes to render each template.

• Use hugo --gc (garbage collection) to clean up unused files, which might help reduce build time.

• Use debug.Timer to determine the execution time of a block of code. And use the hugo --logLevel info info command line flag when you build the site.

{{ $t := debug.Timer "TestSqrt" }}
{{ range seq 2000 }}
  {{ $f := math.Sqrt . }}
{{ end }}
{{ $t.Stop }}

References

Hugo Docs

A higher order function is a function that takes one or more functions as arguments, or returns a function as its result.

These functions are powerful because they allow you to abstract and compose operations in a flexible and reusable way. They are a fundamental concept in functional programming.

Common examples of higher order functions are .map(), .filter(), and reducer().

.map(): Takes a function as an argument and applies it to each element in an array, returning a new array with the results.

const numbers = [1, 2, 3, 4];
const doubled = numbers.map(num => num * 2);
console.log(doubled); // [2, 4, 6, 8]

References

Namaste JS, FreeCodeCamp

Below are the different types of states that can exist within an application. There are three main types:

1. Local State

Local state pertains to a single component. An example of this would be listening to user input in a field or toggling a “show more details” button. Typically, local state is managed within the component using useState or useReducer.

2. Cross-Component State

Cross-component state impacts multiple components. For instance, managing the open/closed state of a modal overlay. While this can also be managed using useState or useReducer, it often involves passing state between components via props drilling.

3. App-Wide State

App-wide state influences the entire application, such as themes or user authentication status. Similar to cross-component state, this can be managed using useState or useReducer, albeit with the assistance of props drilling.

The LISTAGG analytic function, introduced in Oracle 11g Release 2, greatly simplifies string aggregations within SQL queries.

SELECT pid, LISTAGG(ColumnName, ' ' ) WITHIN GROUP (ORDER BY seq) AS ColumnName
FROM B GROUP BY pid;

However, if the output of the above query exceeds 4000 characters, it triggers an error, specifically ORA-01489, indicating that the result of string concatenation is too long.

To address this limitation, Oracle Database Release 2 (12.2) enhanced LISTAGG with the ability to handle overflow errors gracefully, as demonstrated below:

SELECT pid, LISTAGG(ColumnName, ' ' ON OVERFLOW TRUNCATE ) WITHIN GROUP (ORDER BY seq) AS ColumnName
FROM B GROUP BY pid;

In this updated syntax, the output is restricted to 4000 characters, preventing the ORA-01489 error from being raised.

The ON OVERFLOW clause offers several options to manage overflow situations:

• ON OVERFLOW ERROR: This is the default behavior, triggering an error if the result overflows.
• ON OVERFLOW TRUNCATE 'StringYouLike': Appends ‘StringYouLike(Count)’ at the end of the truncated string.
• ON OVERFLOW TRUNCATE '': Displays the first 4000 characters without any additional terminating string.
• ON OVERFLOW TRUNCATE WITH COUNT: Appends the total character count at the end, for example, ‘…(5512)’.

References

Stack Overflow.