Cheat Sheets

SQL

MySQL Cheatsheet

Source: databasestar.com

PostgreSQL Cheatsheet

Source: databasestar.com

Standard SQL Functions Cheat Sheet

The Standard SQL Functions Cheat Sheet provides you with the syntax for different text and numeric functions, CASE WHEN, NULLs, date and time types, INTERVALs, and aggregate functions. The Standard SQL Functions Cheat Sheet has a handy troubleshooting section and plenty of examples.

Source: learnsql.com

SQL Basics Cheat Sheet

Source: learnsql.com

SQL Commands Cheat sheet

Source: intellipaat.com

MongoDB

MongoDB Cheat Sheet

Source : mongodb.com

MongoDB Cheat Sheet

Source : codecentric.de

Quick Cheat Sheet for Mongo DB Shell commands

Source : Michael Treat - GitHub