If you can't remember what every single symbol and operator does in SQL, don't worry -- most of us can't either. That's what cheat sheets are for and Periscope Data has just the thing for the average database developer.
Image: Visual Pharma
As the Periscope Data post itself mentions, searching the web for operators can be difficult, as they're usually eaten by the engine's input sanitisation, resulting incorrect results (or none at all). So instead of hitting up Google, try PD instead.
The cheat sheet starts with the basics -- equality, addition, subtraction, multiplication and so on -- before descending into the more complex. It doesn't delve into regular expression, a massive topic in itself, but it does go over SQL's own string operators, such as concatenation and character matching.
It also covers symbols used in SQL expressions, including type conversion, joins and for Postgres, JSON operators.
If SQL sees constant attention from your keyboard, it a good page to bookmark.
SQL Symbol Cheat Sheet [Periscope Data]