Airtable - Airtable works like a spreadsheet but gives you the power of a database to organize anything. Sign up for free.

Zoho Creator - Zoho Creator is a low-code application development platform that helps you build a custom, mobile-ready apps to run your business.

Sheety - Turn any Google sheet into an API instantly, for free. Power websites, apps, or whatever you like, all from a spreadsheet. Changes to your spreadsheet update your API in realtime. Neat

QuickBase - Quickbase provides a no-code operational agility platform that enables organizations to improve operations through real time insights and automation across complex processes and disparate systems. ​​

Sheetsu - Turn Google Spreadsheet into API

MySQL - The world's most popular open source database