What changed in that query?
Queries get rewritten in review, copied between tools and reformatted by editors, so two versions rarely line up as text. In the example, once both are formatted, the real changes are easy to see: a new c.country column, an inner join turned into a LEFT JOIN (which can change the row count), a widened status filter and a bigger limit.
Pay special attention to JOIN type, WHERE / ON conditions and GROUP BY changes: they change results, while column order and aliases usually don't. For code that embeds SQL, the code compare keeps the surrounding code intact.
Questions
Does SQL compare ignore formatting and keyword case?
With "Format SQL before comparing" on, both queries are reformatted the same way: keywords upper-cased, one clause per line (SELECT, FROM, WHERE, JOIN...), AND/OR on their own lines, and spacing normalised. Differences in layout or keyword case disappear; identifiers, literals and comments are kept exactly.
Does it compare database schemas?
It compares SQL text, so you can compare two schema dumps (CREATE TABLE statements) or two migration files. It does not connect to a database, which also means your data never leaves your browser.
Which SQL dialects work?
The formatter is dialect-neutral and handles standard SELECT/INSERT/UPDATE/DELETE, joins, CTEs and DDL used by PostgreSQL, MySQL, SQL Server, SQLite, BigQuery and Snowflake. Unusual syntax is simply left as written.