Write a sql query to find the second largest number from table table_name and column number.

Write a sql query to delete duplicate rows from a table.

Write a sql query to find the Joining date of Employee in YYYY-DAY-Date format.

You are given this database, your task is to output➡

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If you are starting with SQL and wish to code the queries as you learn more about SQL , Sololearn is perfect place for you.

Here's a snippet of code written in C:

for(int i=0;i<n;i++)
{
 for(int j=0;j<n;j++)
{
//some operation
}
}

How can I write something equivalent in SQL?

Solution:Alias

say, you are asked to count the frequency of each color occurring in the same table , so you can write something like this:


select distinct color ,(select count(*) from colors where c.color=color) from colors c;

When assigning unique identifiers to rows based on a specified order, three key functions come into play: ROW_NUMBER, RANK, and DENSE_RANK.

Consider the following table:

| Name | Score |
|-------- |-------|
| Alice | 90 |
| Bob | 90 |
| Carol | 85 |
| David | 78 |


ROW_NUMBER:

The simplest of the three, ROW_NUMBER assigns a unique number to each row based on the specified order. Each row receives a distinct identifier, incrementing by one.
Example:

1
2
3
4

RANK:

Assigns unique numbers, and in the case of ties, rows get the same rank, and the next rank is skipped.

1
1
3
4

DENSE_RANK:

Assigns ranks to rows with tied values, without skipping the next rank

1
1
2
3

These functions help in organizing and analyzing data by providing distinct identifiers or ranks based on specified criteria. The example table illustrates how ROW_NUMBER, RANK, and DENSE_RANK operate in assigning order to rows with varying scores.

(Note: This is 1/3 of the total number of articles; others are coming soon.)

Question:

Given this data:

id | date | x
1 | 2026-01-01 | 10
1 | 2026-01-05 | 20
1 | 2026-01-10 | 30
1 | 2026-01-15 | 40
1 | 2026-01-20 | 50
2 | 2026-01-02 | 100
2 | 2026-01-06 | 200
2 | 2026-01-11 | 300
2 | 2026-01-16 | 400
2 | 2026-01-21 | 500

Question:
For each id, return the latest 3 dates and their corresponding x values as separate columns.

Expected output:

id | x_1 | x_2 | x_3
1 | 50 | 40 | 30
2 | 500 | 400 | 300


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