GYAAN KUNJA TUITION CENTRE: February 2024

Thursday, February 29, 2024

PHP: write a php code to unzip `.zip` file

Q. Write a php code to unzip `.zip` file

Solution:
<?php

// Specify the path to the zip file
$zipFilePath = 'path/to/sample.zip';

// Specify the directory where you want to extract the contents
$extractPath = 'path/to/output/folder/';

// Create a ZipArchive object
$zip = new ZipArchive;

// Open the zip file
if ($zip->open($zipFilePath) === TRUE) {

    // Extract the contents to the specified directory
    $zip->extractTo($extractPath);

    // Close the zip file
    $zip->close();

    echo 'Extraction successful!';
} else {
    echo 'Failed to open the zip file';
}
?>

Javascript: Image and text merge

Q. I possess both an image and a string, for example, 'Test' and image is 'sample.jpg'. Provide a JAVASCRIPT code that combines the string 'Test' with the image 'sample.jpg', merging them into a single image 'output.jpg'.

Solution:

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Merge Text and Image</title>
</head>
<body>
    <script>
        function mergeTextAndImage(text, imagePath) {
            // Create an HTML image element
            var img = new Image();

            // When the image is loaded, perform the merging
            img.onload = function() {
                // Create a canvas element
                var canvas = document.createElement('canvas');
                var context = canvas.getContext('2d');

                // Set canvas dimensions to match the image
                canvas.width = img.width;
                canvas.height = img.height;

                // Draw the image on the canvas
                context.drawImage(img, -10,-50);

                // Set the text properties
                context.font = '40px Arial'; // You can change the font and size here
                context.fillStyle = 'white'; // Text color

                // Set the position to place the text on the canvas
                var x = 10; // X-coordinate
                var y = 30; // Y-coordinate

                // Draw the text on the canvas
                context.fillText(text, x, y);

                // Create a new image with the merged content
                var mergedImage = new Image();
                mergedImage.src = canvas.toDataURL('image/png');

                // Append the merged image to the body or display it as needed
                document.body.appendChild(mergedImage);
            };

            // Set the source of the image
            img.src = imagePath;
        }

        // Example usage
        var text = 'Test';
        var imagePath = 'path/to/sample.jpg'; // Change this to the path of your image

        mergeTextAndImage(text, imagePath);
    </script>
</body>
</html>

PHP Image and text merge

Q. I possess both an image and a string, for example, 'Test' and image is 'sample.jpg'. Provide a PHP code that combines the string 'Test' with the image 'sample.jpg', merging them into a single image 'output.jpg'.

Solution:

<?php
// Function to merge text and image using default font
function mergeTextAndImage($text, $imagePath, $outputPath) {
    // Load the image
    $image = imagecreatefromjpeg($imagePath);
    // Set the text color Red
    $textColor = imagecolorallocate($image, 255, 0, 0);
    // Set the font size
    $fontSize = 5;

    // Set the position to place the text on the image
    $x = 10; // X-coordinate
    $y = 30; // Y-coordinate

    // Merge text onto the image using default font
    imagestring($image, $fontSize, $x, $y, $text, $textColor);

    // Save the merged image
    imagejpeg($image, $outputPath); // Change this based on your image type

    // Free up memory
    imagedestroy($image);
}

// Example usage
$text = 'Test';
$imagePath = 'sample.jpg'; // Change this to the path of your image
$outputPath = 'output.jpg'; // Change this to the desired output path

mergeTextAndImage($text, $imagePath, $outputPath);
?>
<img src="output.jpg">

Monday, February 19, 2024

Write a psql script to list the columns with `text` datatype

Write a psql script to list the columns with `text` datatype
Answer:

SELECT column_name
FROM information_schema.columns
WHERE table_name = 'myTable'
AND (data_type = 'text' OR data_type = 'character varying');

Problem

Write psql script to find a phase `%abc%123%` in a given table `myTable`.

Answer:

DO $$
DECLARE
    v_column_name text;
    p_table_name text := 'myTable';
    search_pattern text := '%abc%123%';
    query_string text;
BEGIN
    -- Create a dynamic query to search for the pattern in all columns
    FOR v_column_name IN
        SELECT column_name
        FROM information_schema.columns
        WHERE table_name = p_table_name
    LOOP
        query_string := format(
            'SELECT * FROM %I WHERE %I::text LIKE $1',
            p_table_name, v_column_name
        );

        -- Execute the dynamic query
        EXECUTE query_string USING search_pattern;
    END LOOP;
END $$;

Saturday, February 17, 2024

MySQL: Explain RPAD() function in MySQL.

In MySQL, the RPAD() function is used to right-pad a string with a specified set of characters, up to a certain length. This is often used to format strings, ensuring that they have a specific length by adding characters to the right side of the original string.

The basic syntax of the RPAD() function is as follows:

sql
RPAD(str, length, padstr)

str: The original string that you want to right-pad.
length: The length of the resulting string after padding.
padstr: The string or characters to use for padding. This is optional, and if not provided, it defaults to a space.

Here's an example:

sql
SELECT RPAD('123', 5, '0') AS padded_string;

This query will return the string '12300' because the original string '123' is right-padded with zeros to make the total length 5.

If the padstr parameter is not provided, it defaults to a space character. For example:

sql
SELECT RPAD('abc', 6, ' ') AS padded_string;

This query will return the string 'abc ' because the original string 'abc' is right-padded with spaces to make the total length 6.

The RPAD() function is useful in scenarios where you need to format strings to a specific length, such as when dealing with fixed-width data in a table or when creating formatted outputs.

Friday, February 16, 2024

MySQL: Explain LPAD() function in MySQL.

In MySQL, the LPAD() function is used to left-pad a string with a specified set of characters, up to a certain length. This is often used to format strings, ensuring that they have a specific length by adding characters to the left side of the original string.

The basic syntax of the LPAD() function is as follows:

sql
LPAD(str, length, padstr)

str: The original string that you want to left-pad.
length: The length of the resulting string after padding.
padstr: The string or characters to use for padding. This is optional, and if not provided, it defaults to a space.

Here's an example:

sql
SELECT LPAD('123', 5, '0') AS padded_string;

This query will return the string '00123' because the original string '123' is left-padded with zeros to make the total length 5.

If the padstr parameter is not provided, it defaults to a space character. For example:

sql
SELECT LPAD('abc', 6,' ') AS padded_string;

This query will return the string ' abc' because the original string 'abc' is left-padded with spaces to make the total length 6.

The LPAD() function is useful in scenarios where you need to format strings to a specific length, such as when dealing with fixed-width data in a table or when creating formatted outputs.

MySQL: Explain GROUP_CONCAT() function in MySQL.

The GROUP_CONCAT() function in MySQL is used to concatenate values from multiple rows into a single string within each group defined by the GROUP BY clause. It is often used to create a comma-separated list or concatenate strings within each group.

The basic syntax of the GROUP_CONCAT() function is as follows:

sql
GROUP_CONCAT([DISTINCT] expression [ORDER BY {column_name | expr | position} [ASC | DESC] [, ...] [SEPARATOR str_val]])

DISTINCT: Optional keyword to remove duplicate values before concatenation.
expression: The column or expression whose values you want to concatenate.
ORDER BY: Optional clause to specify the order in which values are concatenated within each group.
ASC | DESC: Optional sorting order for the ORDER BY clause.
SEPARATOR: Optional parameter to specify the separator between concatenated values. The default separator is a comma (,).

Here's an example to illustrate the usage of GROUP_CONCAT():

sql
SELECT department, GROUP_CONCAT(employee_name ORDER BY hire_date DESC SEPARATOR ', ') AS employee_list
FROM employees
GROUP BY department;

In this example:

The employee_name values within each department group are concatenated into a single string.
The concatenation is ordered by hire_date in descending order (ORDER BY hire_date DESC).
The values are separated by a comma and space (SEPARATOR ', ').

It's important to note that the GROUP_CONCAT() function is commonly used with the GROUP BY clause. If you use it without grouping, it will aggregate all rows into a single concatenated string.

sql
SELECT GROUP_CONCAT(employee_name ORDER BY hire_date DESC SEPARATOR ', ') AS all_employees
FROM employees;

In this case, it concatenates all employee_name values into a single string for all rows in the employees table.

Be cautious about the length limitations of the result string, as there is a system variable group_concat_max_len that determines the maximum length of the result string produced by GROUP_CONCAT(). If your concatenated string exceeds this limit, you may need to adjust the variable or consider other solutions.

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