Pandas library is the de-facto standard tool for data scientists, nowadays. It is used widely by many data scientists around the globe. After being familiar with it I always use it for processing table-structured data whatever project I am working on. It works fast and reliable, supports CSV, Excel, JSON and so on. However, as a person experienced in , I had some difficulties and confusion with manipulating the tables (a.k.a. DataFrames) in the beginning. Eventually, I learned more APIs and ways of doing the things properly. I believe many people who do his/her first steps on may have the same experience. Some time ago I prepared the cheatsheet using SQL queries and their analogy in Pandas. And I am happy to share it with all of you. SQL Pandas In this post, I am sharing the queries using “SELECT”. I will post other queries and their analogies to Pandas soon later. I would be happy to receive your feedback and wish-list regarding the cheatsheet. Here we go. We have three simple tables: users courses attendance And the rest of the queries will be about data manipulations on them. Lets start from basic SELECT command. SELECT * FROM users SELECT * FROM users LIMIT 0,10 SELECT * FROM users WHERE email IS NULL SELECT first_name, last_name FROM users SELECT DISTINCT birth_year FROM users Basic math and arithmetic operations. SELECT AVG(points) FROM users;SELECT SUM(points) FROM users; Conditional operations and LIKE. SELECT * FROM users WHERE birth_year BETWEEN 1998 AND 2018 SELECT * FROM users WHERE first_name LIKE 'Ch%' SELECT * FROM users WHERE first_name LIKE '%es' SELECT * FROM users WHERE first_name LIKE '%on%' SELECT first_name, last_name FROM users WHERE first_name LIKE '%on%' I finalize this post with JOIN and ORDER BY related SQL queries. To make the code more simpler and easy to read I will assign the results into new variables and re-use them in next ones. SELECT * FROM attendance atnLEFT JOIN users usr ON atn.user_id = usr.id Now lets join the result above with course titles. The result it will be same as the result of following SQL command. SELECT * FROM attendance atnLEFT JOIN users usr ON atn.user_id = usr.idLEFT JOIN courses co ON co.id = atn.course_id The query above will return the full table/dataframe with all columns included. To select necessary columns we can use the same method as we did before. SELECT * FROM users ORDER BY first_name, last_name SELECT * FROM users ORDER BY first_name, last_name DESC SELECT first_name, last_name, birth_year,points, course_name, instructor FROM attendance atnLEFT JOIN users usr ON atn.user_id = usr.idLEFT JOIN courses co ON co.id = atn.course_idORDER BY first_name, last_name
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