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11 Paytm SQL Interview Questions (Updated 2024)

Updated on

March 2, 2024

At Paytm, the leading payments company in India, SQL is typically used for analyzing transactional data for trends and to prevent fraud. That's why Paytm often tests SQL problems during interviews for Data Analyst, Data Science, and BI jobs.

So, to help you prepare for the Paytm SQL interview, we've collected 11 Paytm SQL interview questions – able to solve them?

11 Paytm SQL Interview Questions

SQL Question 1: Get Monthly Average Purchase Amount per User

For Paytm, an online transaction platform, it is important to understand the user behavior such as their spending patterns. Let's assume that Paytm wants to compute the monthly average purchase amount per user. Here, a SQL window function could be useful.

Write a SQL query to retrieve the monthly average purchase amount for each user from the Paytm transactions dataset.

Example Input:
transaction_iduser_idtransaction_dateamount
617112306-08-2022500
780226506-10-2022200
529336206-18-2022300
635219207-26-2022500
451798107-05-2022400
Example Output:
monthuser_idavg_amount
6123500.00
6265200.00
6362300.00
7192500.00
7981400.00

Answer:

‍```sql SELECT EXTRACT(MONTH FROM transaction_date) as month, user_id, AVG(amount) OVER (PARTITION BY EXTRACT(MONTH FROM transaction_date), user_id) as avg_amount FROM transactions ORDER BY month, user_id;


This query starts by filtering the transactions table for records where the month of the transaction date matches the month of interest. It then groups the filtered records by month. For every month, it sums the amount of transactions and multiplies this by 0.02 to calculate the revenue gained from commission. The result is a single record with the month of interest and the total commission revenue for that month.

SQL Question 3: How does and differ?

The clause serves as a filter for the groups created by the clause, similar to how the clause filters rows. However, is applied to groups rather than individual rows.

For example, say you were a data analyst at Paytm trying to understand how sales differed by region:


This query retrieves the total sales for all products in each region, and uses the clause to only sales made after January 1, 2023. The rows are then grouped by region and the clause filters the groups to include only those with total sales greater than $400,000.

Paytm SQL Interview Questions

SQL Question 4: Filter Paytm Customer Transactions

Imagine you are working as a data analyst at Paytm. Your task is to filter down the customer transaction data based on multiple boolean conditions. You need to find all transactions that were done during the month of March and April, for total transaction amounts greater than 500. Also, separate the transactions that were successful from the ones that failed.

Example Input
transaction_idcustomer_idtransaction_datetransaction_amounttransaction_status
10128603/15/2022600Success
10255104/20/2022800Failed
10391704/08/2022300Success
10428602/25/2022700Success
10544203/31/20221000Failed
Example Output:
monthtransaction_statustransaction_id
MarchSuccess101
AprilFailed102
MarchFailed105

Answer:


This SQL query filters the 'transactions' table on the conditions mentioned in the question. The 'EXTRACT' function is used to get the month from the 'transaction_date'. The 'IN' operator is used to check if the month is either March (3) or April (4). Further, we also check if the 'transaction_amount' is greater than 500. Thus, the final output includes the month of transaction, transaction status, and the transaction id that satisfy all these conditions.

SQL Question 5: Do and a typically produce equivalent results?

No, in almost all cases, and for all practical purposes, and do NOT produce the same result.

While both are similar, in that they combine two tables, you can think of joins as increasing the width of the resulting table (you'll have more columns in the result set for a left/inner/right join), whereas a union is used to combine rows which increases the height of the result set but keeps the column count the same.

SQL Question 6: Average transaction amount per user in Paytm

In the Paytm app, each user has an account and can make several transactions such as bill payments, recharges, ticket bookings, etc. As a data analyst, your task is to find the average transaction amount per user. Can you write a SQL query to calculate this?

Please find below the sample tables in markdown format:

Example Input:
transaction_iduser_idtransaction_datetransaction_amount
100112022-10-05500
100222022-10-05150
100312022-10-06200
100432022-10-07100
100512022-10-08300
100622022-10-08200

Answer:

Here is the SQL query that calculates the average transaction amount per user in PostgreSQL:


This query works by grouping all the transactions by the user_id, and then calculates the average transaction amount for each user_id (i.e., each user). The AVG() function in SQL is used to calculate the average. The result of this query will be a list of users along with their average transaction amount.

To practice a very similar question try this interactive Twitter Histogram of Tweets Question which is similar for dealing with user transactions or this Stripe Repeated Payments Question which is similar for handling transaction data.

SQL Question 7: What are SQL constraints, and can you give some examples?

Constraints are used to specify the rules concerning data in the table. It can be applied for single or multiple fields in an SQL table during the creation of the table or after creating using the ALTER TABLE command. The constraints are:

Say you were storing sales analytyics data from Paytm's CRM inside a database. Here's some example constraints you could use:

  • PRIMARY KEY constraint: You might use a PRIMARY KEY constraint to ensure that each record in the database has a unique identifier. For example, you could use the "opportunity_id" field as the primary key in the "opportunities" table.

  • FOREIGN KEY constraint: You might use a FOREIGN KEY constraint to link the data in one table to the data in another table. For example, you could use a foreign key field in the "opportunities" table to reference the "account_id" field in the "accounts" table.

  • NOT NULL constraint: You might use a NOT NULL constraint to ensure that a field cannot contain a NULL value. For example, you could use a NOT NULL constraint on the "opportunity_name" field in the "opportunities" table to ensure that each opportunity has a name.

  • UNIQUE constraint: You might use a UNIQUE constraint to ensure that the data in a field is unique across the entire table. For example, you could use a UNIQUE constraint on the "email" field in the "contacts" table to ensure that each contact has a unique email address.

  • CHECK constraint: You might use a CHECK constraint to ensure that the data in a field meets certain conditions. For example, you could use a CHECK constraint to ensure that the "deal_probability" field in the "opportunities" table is a value between 0 and 100.

  • DEFAULT constraint: You might use a DEFAULT constraint to specify a default value for a field. For example, you could use a DEFAULT constraint on the "stage" field in the "opportunities" table to set the default value to "prospecting"

SQL Question 8: Determining Click-Through Conversion Rate for Paytm

Paytm is an Indian multinational technology company that specializes in e-commerce, digital payment system and financial services. A key analysis for such companies is determining the click-through conversion rate, which measures the success of their digital ads and product placements.

Here's a scenario:

Paytm recently ran digital ads for their new product. Each time a user clicks on an ad, it takes them to the product page on the Paytm website. The data science team at Paytm wants to know the conversion rate, i.e., the proportion of users who add the product to their cart after viewing it from the ad click.

Consider you have two tables. The table records each time a user clicks on the ad, and the table records each time a user adds the item to their cart.

Example Input:
ad_click_iduser_idclick_date
112306/08/2022 00:00:00
226506/10/2022 00:00:00
336206/18/2022 00:00:00
419206/26/2022 00:00:00
598107/05/2022 00:00:00
Example Input:
cart_iduser_idcart_date
20112306/08/2022 00:10:00
20226506/10/2022 01:00:00
20336206/18/2022 02:00:00
20426107/01/2022 00:00:00

Using this data, write a SQL query to calculate the click-through conversion rate for this product. The rate should be calculated as the number of unique users who added the product to their cart, divided by the number of unique users who clicked the ad, expressed as a percentage.

Answer:


Your answer will consist of a single number value indicating the percentage of users who clicked on the ad and also added the product to their cart. A higher value indicates a more successful ad.

To practice another question about calculating rates, try this TikTok SQL question within DataLemur's online SQL coding environment: TikTok SQL question

SQL Question 9: Calculate the Total Transactions Amount for Each User

Paytm is a digital payment platform that lets users transfer money into the integrated wallet via online transactions such as debit, credit, and net banking. Therefore, a good question might be related to understanding user behavior regarding the total transactions amount for each user. You are tasked to find the total transaction amount each user has made.

Example Input:
transaction_iduser_idtransaction_dateamount
1011232022-06-01200
1022652022-06-05500
1031232022-06-03400
1041232022-07-01100
1052652022-07-04200
1069862022-07-09300

The table transactions keeps records of all transactions conducted within Paytm. Here, changes with every new transaction, refers to the person who made the transaction, and refers to the total amount in the transaction.

You need to group by user_id and then use sum() on the amount.

Answer:


Example Output:
user_idtotal_amount
123700
265700
986300

The query performs a summation of the amount per user and then groups the resultant set by user_id.

SQL Question 10: What's the main difference between ‘BETWEEN’ and ‘IN’ operators?

The and operators are both used to filter data based on certain criteria, but they work in different ways. is used to select values within a range, while is used to select values that match a list.

For instance, if you have a table called that contains the salary of each employee, along with which country they reside in, you could use the operator to find all employees who make between 130kand130k and 160k:


To find all employees that reside in France and Germany, you could use the operator:


SQL Question 11: Analysis of Customer Transactions

We have two tables: which provides personal data of customers and which gives information about transactions made by those customers.

Our objective is to get the list of customers who have made transactions above a certain limit (let's say 500) and also get their personal details from the customer_details table. We will use the field to JOIN the two tables.

We are looking to produce a summary table which contains the customer_ID, customer_name, transaction_ID, and the transaction_amount of transactions that have more than $500.

Here are the tables:

Example Input:
customer_idcustomer_namecustomer_emailcontact_number
1John Doejohn.doe@email.com0123456789
2Jane Doejane.doe@email.com9876543210
3Sam Smithsam.smith@email.com1122334455
Example Input:
transaction_idcustomer_idtransaction_datetransaction_amount
111106/08/2022 00:00:00400
222106/10/2022 00:00:001000
333206/18/2022 00:00:00600
444307/26/2022 00:00:00200
555307/05/2022 00:00:00800

Answer:


This SQL statement forms a JOIN operation over two tables, and on the common field . It then filters out the results with transactions more than $500. We will get customer_ID, customer_name, transaction_ID, and transaction_amount in our result.

Since joins come up frequently during SQL interviews, try this interactive Snapchat SQL Interview question using JOINS: Snapchat Join SQL question

Paytm SQL Interview Tips

The best way to prepare for a SQL interview, besides making sure you have strong SQL fundamentals, is to practice a ton of real SQL questions that were asked in recent job interviews. Besides solving the earlier Paytm SQL interview questions, you should also solve the 200+ SQL coding questions which come from companies like Facebook, Google, and VC-backed startups. DataLemur SQL Interview Questions

Each exercise has multiple hints, step-by-step solutions and most importantly, there is an interactive SQL code editor so you can instantly run your SQL query and have it checked.

To prep for the Paytm SQL interview you can also be wise to practice SQL questions from other tech companies like:

But if your SQL query skills are weak, forget about going right into solving questions – strengthen your SQL foundations with this DataLemur SQL Tutorial.

SQL interview tutorial

This tutorial covers SQL concepts such as LEAD/LAG and filtering data with WHERE – both of these pop up frequently during Paytm interviews.

Paytm Data Science Interview Tips

What Do Paytm Data Science Interviews Cover?

In addition to SQL interview questions, the other types of problems tested in the Paytm Data Science Interview are:

Paytm Data Scientist

How To Prepare for Paytm Data Science Interviews?

To prepare for Paytm Data Science interviews read the book Ace the Data Science Interview because it's got:

  • 201 interview questions sourced from FAANG (FB, Apple, Amazon, Netflix, Google)
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