How to learn SQL for data science interview (the minimize effort maximize outcome way)

hey everyone today i'll be talking about how i learned sql from scratch in 11 days to pass my fang data science interview so the situation i had a fang data science interview scheduled in two weeks and i included a significant portion of sql the problem i've literally never touched sql before so today i'll be sharing with you guys how i pass the sql portion of my data science interview while still being a full-time student my motto is always to minimize effort and to maximize outcome so this is a video for people who want to learn sql quickly and pass data science sql interviews specifically after following these steps you'll be able to pass your data science sql interviews and also lay a really strong foundation so that you can actually build upon that and write more complex queries in the future warning this is not a comprehensive guide for how to become amazing at sql this is also not for people who are not motivated to actually put in the effort i can give you my optimized and efficient way of doing things but it's still up to you to put in the work alright so here's what you need a

whiteboard and markers four hours a day for the next 11 days and somewhere you can practice talking through your queries without people thinking you're insane or if you're like me you don't care if people think you're insane and that you're talking to yourself a one and day two is dedicated to figuring out what you have to learn this is a really crucial step data science interviews tend to vary a lot so i only wanted to focus on the questions that they're actually going to ask me instead of just spending a lot of time learning a bunch of different functions or different queries that wouldn't actually help me pass the interview i already scheduled my interview so i knew exactly which company and which position i'll be interviewing for it's totally okay if you don't have interviews scheduled already but do make sure to look at some of the rules and positions and companies that you think you like to work for and you can use those as targets so what's the best way of figuring out what you have to learn first go on glass doors for that exact position in that exact company and look for the sql interview questions as you go through the different questions you'll start to notice that there's actually a lot of repeats this is what i call high impact questions which means that it's going to have a high probability of showing up on your interview and that you definitely have to master if you don't have enough questions from class stores alone don't worry if you literally just type in sql interview questions from position x at company y you'll usually be able to find specific sql interview questions that people post on their blogs were read it finally that's still not enough questions for you go on linkedin and ask people who recently started the position for their sql interview questions i mean what's the harm right the worst that they can say is no or actually the worst they can do is ignore you might think it's kind of weird that i'm asking you to spend your first two days of your precious 11 days not even learning a sequel but figuring out what it is that you should be learning but trust me this is really important these interview questions are going to be your guide for what to learn and also the benchmark for how prepared you are research also shows that priming for questions before you actually know how to solve them ultimately helps you learn faster and retain more the goal for day 3 to 6 is to lay a strong foundational understanding of the sql structure and commonly used sql functions if you learn the right things properly now it will be so much easier for you in the future research shows that deeply understanding the components of something in this case the sql structure and commonly used functions allows you to progress more quickly when you have to put the components together in this case writing the actual sql query that contains a combination of different sql concepts and functions all right so the way that i did this is i went on mode. com which is a free resource for learning the sql fundamentals from my experience this is the best resource for learning sql go through each section from the beginning and intermediate levels also covers sub queries in the advanced section i didn't try to remember all the syntax but i made sure that i really understood what each function exactly does and how it fits into the overall query i also made sure to do all the practice questions that mode gives you so i had a really good understanding not just theoretically but also practically doing the practice questions is key to establishing a strong sql foundation so remember when i said that those real sql interview questions are going to be your guide well make sure to pay special attention to what you saw show up a lot while you were going through the real interview questions also pay extra attention to the joints and how they're different from each other joints tend to show up a lot in sql interviews day seven to eleven time to put the white board to good use also that spot where you can talk to yourself the goal for the next five days is to essentially do the interview twenty plus times following the exact interview style and format i chose to do it this way because research also shows that by practicing the way that you're eventually going to perform in the interview you'll actually end up doing better and also it makes you less nervous because you've essentially just done the interview so many times if you're someone like me and is really prone to being nervous during interviews this is really helpful my strategy for prioritizing interview questions is by going through the questions based upon how many times they appear remember those high impact questions this is how i approach each question one read the question and say any assumptions about the data two write down the steps for the query in english on your whiteboard three write the actual query four evaluate the query and correct any possible mistakes and finally five suggest any possible improvements all right quick pause before i go through the example question i'll just like to remind you that if you find this video useful consider subscribing to the channel every like comment and subscription means a lot to me and really motivates me to make more videos like this alright let's start the example so this is a simpler question that i found on one of the data science interviews on class stores it's totally fine if you don't know what i'm talking about right now but eventually you will just come back to this example when you're ready you're provided a table with page id event timestamp and a flag for state which can be on or off

find the number of pages that are currently on i wrote down versus the table which we're going to call t and it has page id event timestamp and flag so in this case the assumptions that i'm going to make are that page id and event timestamp combined together is the key to this table which means that each combination of page id and event timestamp will be unique i'm also making the assumption that the state of flag has to be on or off step one is to filter by the current time step two is the filter pages that are on and step three is to count number of pages okay so i'm going to write the query i just move that down a little so from t where first filter current time so event timestamp is equal to now and second is filter pages that are on flag is equal to on and third is to count the number of pages so select count as num on and that looks about right to me just looking through it one more time in this case because it's a very simple query there really isn't anything that i can do to improve the efficiency the final step which you wouldn't actually do if you're doing an interview but because we're practicing is to go on sql fiddle where you can put in the dummy data for this table and type out your query and see if it actually runs if there are any errors make a note of it and hold yourself to the highest standard possible of always writing a fully executable query and there you have it your first sql

interview question just like the interview as a note most companies especially tech companies have this kind of whiteboard round that is pretty much exactly like this but for some companies they also have a virtual round before this whiteboard round this is when you have a coder pad that you can see and your interviewer can see and you type your thought process and your query into the coder pad this is pretty similar to the whiteboard in the sense that there's no syntax highlighting and there's no suggestions and you actually can't run the query to test it for most people the virtual format is much easier than the whiteboarding format mostly because you're just more used to typing on a computer so if you practice with a whiteboard from the very beginning like how i did the virtual round is even easier remember minimize effort and maximize output you might also have noticed that it

actually takes quite some time to get through one interview question and that's okay it's way better to get through fewer interview questions but do them really well quality over quantity after i did these sql interview questions for five days i felt really confident and prepared i had learned the foundations of sql very solidly and i essentially just did the interview 20 plus times that's 20 dress rehearsals and there you go that's how i learned sql from scratch in 11 days and passed by sql interview for data science i passed all my interviews and got the job if you follow this plan you'll also be super confident and ready to ace your interview i hope that you found this video helpful and you now feel confident studying sql i'm really curious what you guys think about my sql studying plan let me know in the comments below until next time bye