# 11 Lam Research SQL Interview Questions (Updated 2024)

Updated on

February 6, 2024

At Lam Research, SQL is used across the company for analyzing complex semiconductor manufacturing data and managing huge databases related to chip fabrication process optimization. Because of this, Lam Research asks SQL interview questions during Data Science and Data Engineering job interviews.

So, if you're trying to prepare for the SQL Interview, here’s 11 Lam Research SQL interview questions to practice, which are similar to recently asked questions at Lam Research – can you solve them?

## 11 Lam Research SQL Interview Questions

### SQL Question 1: Identify Top Spending Customers at Lam Research

Lam Research Corporation, a leading supplier of wafer fabrication equipment and services to the global semiconductor industry, maintains a customer database. Your task is to write a SQL query to identify the top 5 customers who have made the highest total purchases of Lam Research products in the last year.

For simplicity, let's assume that the company has the following tables:

###### table:
order_idcustomer_idorder_dateproduct_idquantityprice_per_unit
10130101/15/202120125000
10230203/10/202120513000
10330104/18/202120438000
10430305/20/202120316000
10530206/12/202120242000
10630308/13/202120125000
###### table:
customer_idfirst_namelast_name
301JohnDoe
302JaneSmith
303SamBrown

Write a PostgreSQL query to return the , , , and for the top 5 customers with the highest total purchase amounts in the last year.

This SQL query first performs a JOIN operation on the and tables using the common field. It then filters for orders made in the last year, groups the data by , and calculates the total purchases for each customer. The result is ordered in descending order of , and the clause restricts the output to the top 5 customers.

To solve a related customer analytics question on DataLemur's free online SQL coding environment, try this Microsoft Teams Power User SQL Interview Question:

### SQL Question 2: Calculate the Average Quantity of a Specific Equipment Model Produced Per Month

Lam Research is a company that produces equipment for the semiconductor industry. In this context, you have been given a dataset of the production data for different models in a specific year.

From this dataset, you're tasked to write a PostgreSQL query to calculate the average quantity of a specific equipment model produced per month. Using the window function will help to calculate the monthly average over the entire dataset.

##### Example Input:
prod_idmodelquantityproduction_date
P1M115001/10/2021
P2M210001/15/2021
P3M120002/20/2021
P4M212502/28/2021
P5M19002/27/2021
P6M215003/30/2021
P7M118003/30/2021
##### Example Output:
monthmodelavg_quantity
1M1150.00
1M2100.00
2M1145.00
2M2125.00
3M1180.00
3M2150.00

This query first partitions the data by model and month, and then calculates the average quantity for each partition. It starts by extracting the month from the using the function, and the model from each record. Then the window function is computed over each window defined by the clause, which separates the dataset into windows by and . The result is the average quantity produced for a particular model in a specific month. The final result is sorted by month and model for ease of interpretation.

To practice a similar window function question on DataLemur's free online SQL code editor, solve this Google SQL Interview Question:

### SQL Question 3: In the context of a database transaction, what does ACID mean?

To ensure the reliability and integrity of data, a database management system (DBMS) strives to maintain the ACID properties: Atomicity, Consistency, Isolation, and Durability. To illustrate these concepts, consider the following examples of how ACID properties apply to banking transactions:

1. Atomicity: A transaction is either completed in full or not at all. For example, if a customer is transferring money between accounts, the transaction should either transfer the entire amount or none at all.
2. Consistency: A transaction is only allowed to complete if it follows all rules and constraints within the database. For example, if a customer is withdrawing money from an account, the transaction should only be allowed to proceed if there are sufficient funds available. Otherwise, the transaction is rejected.
3. Isolation: Concurrent transactions are kept separate from each other, so that the changes made by one transaction cannot be seen by another transaction until the first one is complete. This helps prevent conflicts, such as two customers attempting to withdraw money from the same account at the same time.
4. Durability: Once a transaction has been committed and completed, the changes made by the transaction are permanently stored in the database and will not be lost even if the database or system crashes. For example, if a customer makes a deposit, the transaction should be durable so that the deposit is not lost in the event of a system failure.

### SQL Question 4: Lam Research Equipment Maintenance Record Query

Lam Research, a global supplier of innovative wafer fabrication equipment and services to the semiconductor industry, wants to track whenever a piece of equipment undergoes maintenance. They ask you to help design the database for this use case. Assume we have three tables: with equipment id, equipment name and its type; with equipment id, maintenance date, and maintenance duration; and with engineer id, engineer name, and their specialized equipment type.

Sample data for these tables as follows:

##### :
equipment_idequipment_nameequipment_type
1Equipment AType 1
2Equipment BType 2
3Equipment CType 1
##### :
equipment_idmaintenance_datemaintenance_duration
12022-07-013
22022-07-022
12022-07-051
##### :
engineer_idengineer_namespecialized_equipment_type
1Engineer AType 1
2Engineer BType 2
3Engineer CType 1

Write a SQL query that given an equipment type, will return a summary of all the maintenance activities performed on the equipment of that type. The summary should include the equipment id, equipment name, total number of maintenance events, and the total duration of all the maintenance events.

This query first joins the equipment and maintenance tables on the shared equipment_id column. It then selects rows related to the given equipment type. Grouping by the equipment_id and equipment_name ensures unique results per equipment. For each grouped entry, the query counts the total maintenance events and sums up their durations.

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### SQL Question 5: What's a database view, and what's it used for?

A database view is a virtual table that is created based on the results of a SELECT statement, and provides you a customized, read-only version of your data that you can query just like a regular table.

Views in SQL can help you enforce data security requirements by hiding sensitive data from certain users, and can improve performance for some queries by pre-computing the results for an intermediate step and storing them in a view (which can be faster than executing the intermediate query each time). However, their read-only nature means that on any underlying update, the view has to be re-computed.

### SQL Question 6: Filter Customer Database Based on Equipment and Region

Lam Research is a leading supplier of wafer fabrication equipment and services to the global semiconductor industry.

Suppose you are given a database containing a list of all the customers who have purchased equipment from Lam Research. Each customer record includes the customer's id, name, the region where they are located, and the type of equipment they have bought.

The management wants to target a marketing promotion for customers located in the 'EU' region who bought 'etching equipment'. They also want to ignore customers who have already received a promotion in the past.

Write a SQL query to filter out these customers from the customer database. We'll assume the table exists with the following structure:

101ABC CorpEUetching equipmentfalse
103GHI CorpEUcleaning equipmenttrue
104JKL CorpEUetching equipmentfalse
105MNO CorpASetching equipmentfalse

For this question, your output should be:

101ABC CorpEUetching equipmentfalse
104JKL CorpEUetching equipmentfalse

This SQL script uses the WHERE clause to filter the customers based on multiple boolean conditions: the region must be in the 'EU', the equipment type must be 'etching equipment', and the customer should not have received a promotion before. The output will be the list of customers who meet all these conditions. undefined

### SQL Question 7: What's the major difference between and ?

The clause is used to filter the groups created by the clause. It's similar to the clause, but it is used to specify conditions on the groups created by the clause, rather than on the individual rows of the table.

For example, say you were analyzing salaries for analytics employees at Lam Research:

This query retrieves the total salary for each Analytics department at Lam Research and groups the rows by the specific department (i.e. "Marketing Analytics", "Business Analytics", "Sales Analytics" teams).

The clause then filters the groups to include only Lam Research departments where the total salary is greater than \$1 million

### SQL Question 8: Average Production Cycle Time

Lam Research is a company that specializes in the design, manufacturing, and servicing of wafer fabrication equipment and services to the semiconductor industry. An interesting question could be:

"Find the average production cycle time of all equipments manufactured by Lam Research."

##### Example Input:
cycle_idequipment_idstart_timeend_time
1021E56705/01/2022 07:00:0005/02/2022 07:00:00
1045E78906/04/2022 08:00:0006/05/2022 08:30:00
1073E56707/10/2022 09:00:0007/11/2022 09:00:00
1084E12308/08/2022 06:00:0008/09/2022 06:30:00
1102E78909/07/2022 08:00:0009/08/2022 08:15:00

This query extracts the difference between and of each manufacturing cycle for every equipment_id, which gives the duration of the production cycle. By using the output will be the total number of seconds in that time interval. To convert seconds into hours we divide it by 3600. The aggregate function is then used to find the average production cycle time for each equipment.

To practice a very similar question try this interactive Amazon Server Utilization Time Question which is similar for querying time calculations or this Tesla Unfinished Parts Question which is similar for querying a manufacturing process.

### SQL Question 9: Retrieve Customer Data with Specific Equipment Type

Lam Research is a leading company supplying equipment and services for fabricating semiconductor devices. As an SQL developer, you are tasked with extracting customer details who are using a particular type of equipment from Lam Research. The equipment type name starts with "Etch".

Write a SQL query to retrieve the customer details from a customer records table whose equipment type begins with "Etch".

Here is an example of a table:

##### Example Input
customer_idcustomer_nameinstallation_dateequipment_type
1Intel Corp2021-08-15Etch Tool Series 1
2AMD Group2021-06-25Deposition System Series 3
3Apple Inc.2021-09-10Etch Tool Series 2
4Samsung Electronics2021-11-05Metrology System Series 2
5TSMC Corp2021-12-20Etch Tool Series 1

This query uses the keyword in SQL along with the wildcard to filter out the records where equipment_type starts with 'Etch'. The acts as a wildcard that can match any string following 'Etch'. undefined

### SQL Question 10: What do primary keys do?

The primary key of a table is a column or set of columns that serves as a unique identifier for each row. It ensures that all rows are distinct and does not allow null values.

For example, say you had stored some Facebook ad campaign data that Lam Research ran:

The CampaignID column is used to uniquely identify each row in the table, and the constraint ensures that there are no duplicate CampaignID values. This helps to maintain the accuracy of the data by preventing duplicate rows. The primary key is also an important part of the table because it enables you to easily identify and reference specific campaigns in your Facebook Ad data. You can use it to join to other tables in the database, such as a table with data on the results of the campaigns.

### SQL Question 11: Average Manufacturing Time per Semiconductor Type

Lam Research, a company that specializes in semiconductor production, wants to optimize its manufacturing process by understanding the time taken to manufacture different types of semiconductors which may vary due to complexity, different production processes and machinery time utilization. You've been given the raw data of semiconductor manufacturing with the start and end time of production. Write an SQL query to calculate the average manufacturing time per semiconductor type. For simplicity's sake, we define manufacturing time as the ABSOLUTE difference between end time () and start time (), assuming they are UNIX timestamps. Please ROUND this value to nearest integer.

##### Example Input:
semiconductor_idsemiconductor_typestart_timestampend_timestamp
1Type_A16225200001622523600
2Type_A16225236001622527200
3Type_B16225272001622530800
4Type_B16225308001622534400
5Type_A16225380001622541600
##### Example Output:
semiconductor_typeavg_manufacturing_time
Type_A3600
Type_B3600

In this query we are using the GROUP BY statement to organize the data by the semiconductor type. For each type, we calculate the absolute difference between the end time and the start time of manufacturing. We then calculate the average of these times (using the AVG function), and round this number to the nearest whole number (using the ROUND function). The resulting output gives us the average manufacturing time for each type of semiconductor.

To practice a very similar question try this interactive Tesla Unfinished Parts Question which is similar for analyzing manufacturing processes or this Amazon Server Utilization Time Question which is similar for calculating duration.

### Lam Research 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. In addition to solving the earlier Lam Research SQL interview questions, you should also solve the 200+ SQL questions from real Data Science & Analytics interviews which come from companies like FAANG (FB, Apple, Amazon, Netflix, Google).

Each SQL question has hints to guide you, detailed solutions and most importantly, there is an interactive coding environment so you can easily right in the browser your query and have it graded.

To prep for the Lam Research SQL interview it is also wise to solve SQL problems from other tech companies like:

However, if your SQL foundations are weak, don't worry about diving straight into solving questions – go learn SQL with this free SQL tutorial.

This tutorial covers things like working with string/text data and grouping by multiple columns – both of these come up frequently in SQL job interviews at Lam Research.

### Lam Research Data Science Interview Tips

#### What Do Lam Research Data Science Interviews Cover?

For the Lam Research Data Science Interview, beyond writing SQL queries, the other types of questions to practice:

• Statistics and Probability Questions
• Coding Questions in Python or R
• Business Sense and Product-Sense Questions
• ML Modelling Questions
• Resume-Based Behavioral Questions

#### How To Prepare for Lam Research Data Science Interviews?

The best way to prepare for Lam Research Data Science interviews is by reading Ace the Data Science Interview. The book's got:

• 201 Interview Questions from companies like Google, Tesla, & Goldman Sachs
• A Refresher covering Stats, SQL & ML
• Amazing Reviews (900+ reviews, 4.5-star rating)