# 10 Alaska Air SQL Interview Questions (Updated 2024)

Updated on

June 30, 2024

At Alaska Air, SQL used for analyzing flight data, and managing passenger booking records so they can deliver the best service possible. Because of this, Alaska Air almost always evaluates jobseekers on SQL problems during interviews for Data Science, Analytics, and & Data Engineering jobs.

## 10 Alaska Air SQL Interview Questions

### SQL Question 1: Flight Load Analysis With Window Functions

As a data analyst at Alaska Air, you are tasked to analyze flight load over the past year. Flight load factor is an important metric showing the percentage of available seating capacity that is filled with passengers.

Each row in the table represents a flight with , departure , the number of and of the plane.

Your task is to write a SQL query that calculates the monthly average load factor for each flight code over the last year. The load factor for a single flight is defined as .

##### Example Input:
flight_codedatepassengerscapacity
AS10101/15/2022120150
AS10101/30/2022130150
AS10202/15/2022110150
AS10102/22/2022145150
AS10202/30/2022120150
AS10103/03/2022130150
AS10203/07/2022100150
##### Expected Output:
1AS10183.33
2AS10191.67
2AS10276.67
3AS10186.67
3AS10266.67

The PostgreSQL query for this problem using window function might look something like this:

This query is extracting the month from the date of each flight, then calculating the average load factor for each flight_code for each month over the last year. The result will be sorted by month and flight_code.

To practice a related window function SQL problem on DataLemur's free interactive SQL code editor, solve this Google SQL Interview Question:

### SQL Question 2: Department vs. Company Salary

Imagine there was a table of Alaska Air employee salaries, along with which department they belonged to. Write a query to compare the average salary of employees in each department to the company's average salary. Return the comparison result as 'higher', 'lower', or 'same' for each department. Display the department ID, payment month (in MM-YYYY format), and the comparison.

Code your solution to this interview question and run your code right in DataLemur's online SQL environment:

The solution is LONG – 30+ lines of SQL. You can find a step-by-step solution here: Department vs. Company Salary.

### SQL Question 3: What are database views 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 4: Flight Occupancy Analysis

Alaska Airlines has several flights flying various routes on different days of the week. The company wants to know the occupancy rate of each flight to optimize its schedule. The occupancy rate is defined as the number of sold seats divided by the number of total seats on the flight.

Also check out the Alaska Airlines key reports to see how many seats they have booked in the past!

You are provided with two tables:

table contains information about each flight: id of the flight, total number of seats and the date of the flight.

##### Example Input:
flight_idtotal_seatsflight_date
120006/08/2021
215006/09/2021
330006/10/2021
425006/11/2021
520006/12/2021

table contains information about each booked seat: id of the booking, id of the flight and the date of booking.

##### Example Input:
booking_idflight_idbooking_date
1106/01/2021
2206/02/2021
3106/03/2021
4306/03/2021
5306/04/2021

Please write a SQL query to calculate occupancy rate for each flight in the table.

Each row in the bookings table represents one seat booked on a flight. To get the number of seats sold for a flight, we count the number of bookings for that flight. We then divide this by the total number of seats on the flight to get the occupancy rate. Note that we need to multiply by 1.0 to ensure that the division is not integer division. The ensures that we include flights that have no bookings (i.e, zero occupancy rate).

### SQL Question 5: When would you use a clustered index vs. a non-clustered index?

Here's an example of a clustered index on the column of a table of Alaska Air payments table:

This creates a clustered index on the column, which will determine the physical order of the data rows in the table.

Here is an example of a non-clustered index on the column of the same table:

This will create a non-clustered index on the column, which will not affect the physical order of the data rows in the table.

In terms of query performance, a clustered index is usually faster for searches that return a large number of records, while a non-clustered index is faster for searches that return a small number of records. However, updates to a clustered index are slower, as they require the data rows to be physically rearranged, while updates to a non-clustered index are faster, as they only require the index data structure to be updated.

### SQL Question 6: Find the Average Flight Delay

As a data analyst at Alaska Air, you're asked to find the average flight delay in minutes for each origin airport over the past year. The table has a , , and .

Assume that if is less than , then the difference is treated as flight delay (in minutes), otherwise there was no delay.

##### Example Input:
flight_idorigin_airportscheduled_departure_dateactual_departure_date
1001SEA07/08/2021 10:00:0007/08/2021 10:15:00
1002SFO07/08/2021 12:30:0007/08/2021 12:30:00
1003SEA07/09/2021 16:00:0007/09/2021 17:00:00
1004SFO07/10/2021 14:45:0007/10/2021 15:45:00
1005SEA07/11/2021 19:20:0007/11/2021 19:30:00

This SQL query first calculates the delay time in minutes for each delayed flight using . The function then calculates the average delay time for each origin airport with the help of the clause.

To practice a very similar question try this interactive Amazon Average Review Ratings Question which is similar for requiring average calculation from time-stamped data or this Alibaba Compressed Mean Question which is similar for dealing with averaging logistics data.

### SQL Question 7: Can you explain the concept of a constraint in SQL?

SQL constraints are used to specify rules for the data in a table. They can be applied to single or multiple fields in a table when the table is created, or after the table has been created using the ALTER TABLE command.

Here's what some constraints could look like:

Alaska Air implements digital ads to attract potential customers to book flights from their website. They are interested to know the click-through-rate of their ads per day, as this will provide them insight on the effectiveness of their ads.

• Click, which is an action where potential customers click the digital ads.
• Views, potential customers being drawn to the digital ads.
• Date, the date when the action occurred.

Assume you're given a table named with the following structure:

##### Example Input:
12022-07-013005000
22022-07-022504800
32022-07-032604600
42022-07-043505500
52022-07-052004900
62022-07-062705100

Create a SQL query to determine the daily click-through-rate of Alaska Air's digital ads.

The click-through-rate can be calculated by the number of clicks divided by the number of views. Here's the SQL query which solves the question:

This query will give us the daily click-through-rate, it divides the number of clicks by the number of views to find the click-through-rate for each day.

##### Expected Output:
dateclicksviewsclick_through_rate
2022-07-0130050000.06
2022-07-0225048000.0521
2022-07-0326046000.0565
2022-07-0435055000.0636
2022-07-0520049000.0408
2022-07-0627051000.0529

To practice a similar SQL interview question on DataLemur's free interactive SQL code editor, solve this SQL interview question asked by Facebook:

### SQL Question 9: Average Flight Delay by Route

Given the table showing departure times, arrival times, and delay for each flight by route, write a query to calculate the average delay for each route for Alaska Air.

##### Example Input:
flight_idroute_iddeparture_timearrival_timedelay_minutes
11002022-06-08 06:002022-06-08 08:0030
22002022-06-10 10:002022-06-10 14:0020
31002022-06-18 12:002022-06-18 14:0045
43002022-07-26 06:002022-07-26 09:0015
52002022-07-05 16:002022-07-05 20:0025

This SQL statement groups all the flights by route_id and calculates the average delay per route. Using the GROUP BY clause, the result-set by route_id will be grouped. The AVG function calculates the average value for the delay_minutes column for each grouped record.

### SQL Question 10: Can you explain the purpose of the constraint and give an example of when you might use it?

The CHECK constraint is used to set a rule for the data in a column. If a row is inserted or updated and the data in the column does not follow the rule specified by the CHECK constraint, the operation will be unsuccessful.The CHECK constraint is often used in conjunction with other constraints, such as NOT NULL or UNIQUE.

You might consider implementing the CHECK constraint in your database if you want to ensure that certain data meets specific conditions. This can be helpful for maintaining the quality and reliability of your data.

For example, you might use a CHECK constraint to ensure that a column contains only positive numbers, or that a date is within a certain range.

### Alaska Air SQL Interview Tips

The key to acing a Alaska Air SQL interview is to practice, practice, and then practice some more! Beyond just solving the above Alaska Air SQL interview questions, you should also solve the 200+ DataLemur interview questions which come from companies like Microsoft, Google, Amazon, and tech startups.

Each DataLemur SQL question has multiple hints, full answers and most importantly, there's an online SQL code editor so you can right in the browser run your SQL query answer and have it graded.

To prep for the Alaska Air SQL interview it is also a great idea to practice SQL questions from other airlines like:

But if your SQL skills are weak, forget about jumping right into solving questions – go learn SQL with this SQL tutorial for Data Scientists & Analysts.

This tutorial covers topics including RANK vs. DENSE RANK and handling NULLs in SQL – both of these come up routinely during SQL interviews at Alaska Air.

### Alaska Air Data Science Interview Tips

#### What Do Alaska Air Data Science Interviews Cover?

In addition to SQL query questions, the other types of problems covered in the Alaska Air Data Science Interview include:

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