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How to Create a Symmetric Array in Python: A Fun Logic Exercise

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 Here's a Python program that says to write a Symmetric array transformation. A top interview question. Symmetric Array Transformation Problem: Write a Python function that transforms a given array into a symmetric array by mirroring it around its center. For example: Input: [1, 2, 3] Output: [1, 2, 3, 2, 1] Hints: Use slicing for the reverse part. Concatenate the original array with its mirrored part. Example def symmetric_array(arr):     """     Transforms the input array into a symmetric array by mirroring it around its center.     Parameters:     arr (list): The input array.     Returns:     list: The symmetric array.     """     # Mirror the array by concatenating the original with its reverse (excluding the last element to avoid duplication)     return arr + arr[-2::-1] # Example usage input_array = [1, 2, 3] symmetric_result = symmetric_array(input_array) print("Input Array:", input_arr...
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How to Resolve ORA-01722 Invalid Number Error in Oracle SQL Developer

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When working with Oracle SQL Developer, you may come across an error message that reads "ORA-01722: invalid number". This error can be frustrating and difficult to understand, especially if you're new to SQL. In this post, I will explain the cause of this error and provide a solution to resolve it.


Invalid Number Error


Cause of the Error - ORA-01722


Let's consider an example where we have two tables named "my_hr" and "my_dept". The "my_hr" table contains three columns - "name", "pay_id", and "user_id", while the "my_dept" table contains two columns - "name" and "user_id".

CREATE TABLE my_hr (
name CHAR(20),
pay_id NUMBER,
user_id CHAR(6)
);

CREATE TABLE my_dept (
name CHAR(20),
user_id CHAR(6)
);

Now, let's insert some sample data into these tables:

INSERT INTO my_hr VALUES ('Srini', 567, '123456');
INSERT INTO my_dept VALUES ('Srini', '123456');

If we try to execute the following SELECT query to join these two tables using the "name" and "user_id" columns and filter the results based on the "pay_id" column, we will get the "ORA-01722: invalid number" error:

SELECT *
FROM my_hr a, my_dept b
WHERE name = 'Srini'
AND pay_id = '123456' -- This causes the error
AND a.user_id = b.user_id;

The reason for this error is that we are comparing a number column "pay_id" with a string literal value ('123456').

Solution to Resolve the Error:


To fix the error, we need to make sure that we are comparing the "pay_id" column with a number value instead of a string. We can do this by removing the single quotes from the value we are comparing:

SELECT *
FROM my_hr a, my_dept b
WHERE name = 'Srini'
AND pay_id = 123456 -- This is the corrected version
AND a.user_id = b.user_id;

By removing the single quotes from the value of the "pay_id" column, we can compare it with the number column correctly.

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