sqlize.online is described as 'SQLize.online is a free online SQL environment for quickly running, experimenting with and sharing SQL code'. There are five alternatives to sqlize.online, not only websites but also apps for Self-Hosted solutions. The best alternative is SQL Fiddle, which is both free and Open Source. Other great sites and apps similar to sqlize.online are phpize.online (Free), Online SQL Editor (Freemium), DB Fiddle (Free) and db<>fiddle (Free).
The Online SQL Editor provides you with real-time Business Intelligence on a large number of cloud platforms. It allows you to extract and analyze data, stored in the cloud of Exact Online, JIRA, Freshdesk, GitLab, Nmbrs, Salesforce and others.