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Lesson 16
Courses / HackerRank SQL Problem Solving Solution Challenges
Weather Observation Station 16 | SQL Aggregation | HackerRank Solution

Summary

Weather Observation Lesson Summary

In this lesson, we're focusing on querying a database for weather observation data. Here's a concise breakdown of the key points discussed:

Database Table

  • Table Name: station
  • Columns:
    • ID
    • city
    • state
    • lat_n
    • long_w

Objective

  • Task: Query the smallest lat_n value that is greater than 38.778.
  • Output Requirement: Round the result to four decimal places.

Steps to Achieve the Query

  1. Visualize the Data:

    • Execute the command: SELECT * FROM station;
    • Focus on the lat_n column values.
  2. Filter and Find Minimum:

    • Use a WHERE clause to filter lat_n for values greater than 38.778.
    • Retrieve the smallest value:
      • Use MIN(lat_n) to find the minimum latitude after filtering.
  3. Round the Result:

    • Apply the ROUND function to format the result to four decimal places.

Final Result

  • The query yields: 38.8526 (rounded to four decimal places).

This method effectively identifies the smallest latitude from the selected observations over the specified threshold.

Video Transcript

Hey everybody, welcome back to another lesson. I will do weather observation, station 16 on the section aggregation from SQL Hacker Rink. We're given the table station that has five columns ID, city, state, lat, underscore, n, long underscore, w. We're asked to query the smallest lat underscore, n that is greater than 38.778. So around the answer to four decimal places. Okay, so let's get started. So I always like to visualize the data. So I say select star from station, run code. Okay, so here for the purposes of this question, we only care about the column, lat, underscore, n, these values here. So for the range that's greater than 38.778, what value is the lowest, right? You have to find the lowest out of all these numbers. So let's go. We here have to say, aware. First, lat underscore n has to be greater than 38.778. And then we have to take, okay, so we have the lat underscore n values. And we have to take the smallest. And for that, we could do an order by and take only the row of the smallest. The first one if you do ascending, or you could use the function min. So I'm gonna use min of lat underscore n. So out of all the values that were found, it takes the smallest one. And because we want to round the answer to four decimal places, if you think this is one thing that's the actual value of the min, you have to say round for the function call. And two decimal places has to be four here for four decimal places. And there you go, we have 38.8526, exactly four digits to the right-hand side of the decimal point, and it was being rounded. And that's weather observation station 16.
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