Remove Redundant Pairs - SQL Interview Query 1 | SQL Problem Level "HARD"

techTFQ
1 Mar 202419:58
EducationalLearning
32 Likes 10 Comments

TLDRThe speaker announces the commencement of a 30-day SQL query challenge, where they will post daily videos covering various SQL interview queries. The queries are sourced from multiple platforms and range from basic to complex levels. The first query involves removing redundant pairs from a given input table based on specific conditions related to custom fields. The speaker uses PostgreSQL and the PGAdmin tool to demonstrate the solution, creating a pair ID to identify and process the data accordingly. They encourage viewers to download the dataset, attempt the challenge, and share their solutions on a dedicated Discord channel for collaborative learning and problem-solving. The ultimate goal is to foster a supportive community to help each other through the 30-day challenge.

Takeaways
  • 📅 The speaker is starting a 30-day SQL query challenge, posting a video each day covering an SQL interview query.
  • 🔗 Queries are sourced from various platforms, including LinkedIn, Discord, and online platforms like Stack Overflow.
  • 📈 The complexity of the queries will vary from basic to complex levels.
  • 🔍 The first query involves removing redundant pairs from an input table based on certain conditions.
  • 🧩 The problem requires identifying pairs of brands within the same year and then applying conditions to keep or remove records.
  • 📝 The solution involves creating a unique 'pair ID' for each pair of brands using a combination of the 'brand one', 'brand two', and 'year'.
  • 🔑 A 'CASE' statement is used to determine the order of brands when creating the 'pair ID'.
  • 📊 The 'ROW_NUMBER()' window function is used to assign a unique row number to each record within a pair.
  • ✅ A filter condition is applied to return records where the row number is one or where custom fields do not match.
  • 💡 The final output includes records that meet the specified conditions, effectively removing redundant pairs.
  • 🤝 The speaker encourages participants to share their solutions on Discord and build a community to help each other.
  • 🚀 The challenge aims to build a community on Discord where participants can discuss, share solutions, and learn from each other.
Q & A

  • What is the purpose of the 30-day SQL query challenge?

    -The purpose of the 30-day SQL query challenge is to post a video every day for 30 days, each covering a different SQL interview query. The challenge aims to help participants improve their SQL skills by solving real interview queries.

  • Where can one find the data set for the challenge?

    -The data set for the challenge can be found on the presenter's blog or on their Discord server. Links to both resources are provided in the video description.

  • What are the different levels of complexity for the queries in the challenge?

    -The queries in the challenge vary in complexity, ranging from basic to intermediate and complex levels.

  • What is the first query of the challenge about?

    -The first query is about removing redundant pairs from a given input table based on certain conditions related to the values in custom fields and the year associated with each brand pair.

  • How does the presenter suggest identifying pairs of brands in the input table?

    -The presenter suggests identifying pairs by creating a unique 'pair ID' for each pair by concatenating the 'brand one', 'brand two', and 'year' columns, ensuring that pairs belonging to the same year and having interchanged brand names are assigned the same pair ID.

  • What is the first condition given for deciding which records to keep in the final output?

    -The first condition is that if the 'custom one' field is equal to 'custom three' and 'custom two' is equal to 'custom four', then only one pair should be kept in the final output.

  • What is the second condition for deciding which records to keep?

    -The second condition is that if 'custom one' is not equal to 'custom three' or 'custom two' is not equal to 'custom four', then both pairs should be kept in the final output.

  • What is the third condition mentioned in the problem statement?

    -The third condition is that for brands that do not have pairs in the same year, those rows should be kept in the final output.

  • How does the presenter plan to solve the problem of identifying and removing redundant pairs?

    -The presenter plans to use a combination of SQL techniques, including concatenation to create pair IDs, the CASE statement for conditional logic, and the ROW_NUMBER() window function to assign unique row numbers to each pair, which will help in applying the given conditions to filter the final output.

  • What tool is the presenter using to solve the SQL query challenge?

    -The presenter is using PostgreSQL database and the PGAdmin tool to solve the SQL query challenge.

  • How can participants share their solutions and discuss the challenge?

    -Participants can share their solutions and discuss the challenge on the presenter's Discord server, specifically in a channel created for the 30-day SQL query challenge.

  • What is the presenter's hope for the community participating in the challenge?

    -The presenter hopes to build a community on Discord where participants can help each other solve the 30 problems presented in the challenge, share different solutions, and learn from one another.

Outlines
00:00
🚀 Introduction to the 30-Day SQL Query Challenge

The speaker introduces a 30-day SQL query challenge where they will post daily videos covering various SQL interview queries. The queries are sourced from multiple platforms and range from basic to complex levels. The first video focuses on a query to remove redundant pairs from an input table based on certain conditions. The speaker explains the structure of the input table and the problem statement, which involves identifying pairs of brands in the same year and applying specific conditions to determine which records to keep in the final output.

05:01
🔍 Understanding and Solving the Query

The speaker delves into solving the first query by first creating a unique pair ID for each pair of brands in the same year. They use a combination of concatenation and conditional logic to ensure that pairs are correctly identified. The speaker then discusses the three conditions that need to be met for the final output: removing one record from a pair if certain fields match, keeping both records of a pair if the fields do not match, and keeping records of brands without pairs. They encourage viewers to download the dataset, attempt the query with their preferred SQL database, and share their solutions on a dedicated Discord channel for discussion and assistance.

10:02
📈 Implementing the Solution with PostgreSQL

The speaker chooses to use PostgreSQL and the PGAdmin tool to solve the query. They create a table with the given data and then proceed to find pairs of brands using a combination of concatenation and a CASE statement to handle the order of brand names. The speaker uses a Common Table Expression (CTE) to assign a unique pair ID to each record and then applies the ROW_NUMBER() window function to identify which records to keep based on the given conditions. The final step involves filtering the records to meet the specified conditions and presenting the desired output.

15:03
🤝 Engaging the Community and Wrapping Up

The speaker emphasizes the importance of community engagement and invites viewers to participate in the challenge by sharing their solutions and discussing different approaches on Discord. They provide a link to their blog and Discord server for accessing the dataset and further information. The speaker concludes by executing the final query, which produces the expected output, and encourages viewers to like, share, and spread the word about the 30-day SQL query challenge. They look forward to continuing the challenge with the next query in the following video.

Mindmap
Keywords
💡SQL Query Challenge
The SQL Query Challenge is a 30-day event where the host posts a new SQL interview query each day. It serves as an interactive way to improve SQL skills and tackle real-world database problems. The challenge is designed to engage the audience in solving queries of varying complexity, from basic to complex, and is part of the video's main theme.
💡PostgreSQL
PostgreSQL, often abbreviated as Postgres, is an open-source relational database management system (RDBMS) that the host uses to demonstrate the solution to the SQL challenge. It is known for its robustness and support for advanced SQL features, which makes it a popular choice for complex database tasks.
💡Discord
Discord is a communication platform where the host has set up a server for the SQL challenge. It is used as a community hub where participants can download datasets, share their solutions, ask for help, and discuss different approaches to solving the SQL queries. It plays a key role in fostering a collaborative learning environment.
💡Pair ID
In the context of the video, a Pair ID is a unique identifier created for each pair of brands within the same year. It is generated by concatenating the brand names and year, and is used to identify and manipulate data related to specific pairs in the SQL query. The concept of Pair ID is central to solving the challenge presented in the video.
💡Window Function
A window function in SQL is used to perform calculations across sets of rows that are related to the current row. In the video, the ROW_NUMBER() window function is applied to assign a unique sequential integer to each row within a partition of the result set, which is then used to filter out redundant pairs based on the given conditions.
💡Concatenation
Concatenation in SQL is the process of combining two or more strings of text to create a single string. In the video, concatenation is used to create a unique 'Pair ID' by combining the brand names and year, which is essential for identifying duplicate pairs and applying the conditions to filter the data.
💡Custom Fields
Custom fields refer to the additional columns in the input table that contain specific data related to the brands. In the context of the video, custom fields are used to determine whether a pair of brand records should be kept or removed based on the conditions that compare the values of these fields.
💡Row Number
The row number is a sequential integer assigned to each row retrieved by a query. In the video, the row number is used in conjunction with window functions to identify and filter out redundant pairs of brand records according to the specified conditions, ensuring that only necessary records are included in the final output.
💡CTE (Common Table Expression)
A CTE, or Common Table Expression, is a temporary result set that you can reference within a SELECT, INSERT, UPDATE, or DELETE statement. In the video, the host uses a CTE to create a derived table that includes a row number for each record, which aids in applying the filtering conditions to achieve the desired output.
💡Filter Condition
A filter condition in SQL is a clause that restricts the rows returned by a query to those that meet certain criteria. In the video, the host uses filter conditions to implement the logic for removing redundant pairs and to ensure that only the required records are included in the final result set based on the challenge's conditions.
💡Dataset
The dataset refers to the structured input data used for the SQL challenge. It includes a table with brand information and custom fields that participants use to practice their SQL skills. The dataset is essential for the challenge as it provides the context and data required to solve the given query.
Highlights

The start of a 30-day SQL query challenge with daily video posts covering one SQL interview query each day.

Queries are sourced from various platforms, including user submissions, online platforms, and personal creation.

The complexity of the queries ranges from basic to complex levels.

The first query focuses on removing redundant pairs from a given input table.

The problem statement involves identifying pairs of brands in the same year and applying specific conditions to keep or remove records.

A method to create a unique pair ID by concatenating brand names and year, taking into account the alphabetical order.

Using a CASE statement to handle the comparison between brand names for pair ID creation.

The utilization of the ROW_NUMBER() window function to assign unique identifiers to each record within a pair.

Filtering records based on the row number and custom field conditions to meet the problem statement's requirements.

The final output includes specific records from each pair based on the given conditions, ensuring no redundant data.

The process of solving the query using PostgreSQL and the PGAdmin tool.

Invitation to the audience to download the dataset, attempt the query, and share solutions on the Discord server.

Emphasis on building a community on Discord to help each other solve the 30 challenges.

The importance of reviewing different solutions and understanding various approaches to the same problem.

The speaker provides a step-by-step explanation of their thought process and the SQL query used to solve the challenge.

The final SQL query provided to achieve the desired output, adhering to the conditions of the problem statement.

Encouragement for viewers to participate in the 30-day SQL query challenge and engage with the community for mutual learning.

Transcripts

Browse More Related Video

SQL Mock Interview (Data Analyst): Departments with the Highest Revenues

I did this for 30 days and it improved my photography.

SQL interview questions and answers | Entry level data analyst interview

Can you crack these 2 logical puzzles?

Analyze a User's Posts - Data Analyst SQL Mock Interview

If You Want More From Someone Who’s Not Ready DO NOT CHASE Do THIS Instead

Rate This

5.0 / 5 (0 votes)

Thanks for rating:

Related Tags
SQL ChallengeInterview QueriesCommunity SupportSkill DevelopmentData AnalysisCoding PracticeDatabase ManagementPostgreSQLPGAdminDiscord ServerLinkedIn