How to compare two SQL queries and spot the logic change

In the example, the second query was rewritten with lowercase keywords and two real edits: the filter now includes refunded orders, and the limit changed. As typed, the tool reports 1 change: 7 lines removed, 7 added, since every keyword changed case. With Ignore case on, it reports 2 changes: 2 lines removed, 2 added. Those are the where line and the limit line.

SQL keywords don't depend on case, so for keyword style the switch is safe. Names and string values are another matter. MySQL on Linux can treat table names as case sensitive, and whether 'paid' and 'Paid' match the same rows depends on the database and its collation. Ignore case hides those changes too, so read the quoted values with the switch off before you sign off on a query.

Formatting is the other big source of noise. If one query is on a single line and the other puts each clause on its own line, nearly everything differs. Run both through the same formatter, or split them by hand at each keyword like FROM, JOIN, WHERE and ORDER BY. Ignore whitespace then takes care of different indentation.

Here's the patch the tool gives with case ignored:

--- a/paid-orders.sql
+++ b/paid-orders.sql
@@ -1,7 +1,7 @@
 SELECT o.id, o.total, c.email
 FROM orders o
 JOIN customers c ON c.id = o.customer_id
-WHERE o.status = 'paid'
+where o.status in ('paid', 'refunded')
   AND o.created_at >= '2026-01-01'
 ORDER BY o.created_at DESC
-LIMIT 50;
+limit 100;