Version:

constant ER_DUP_ENTRY

Ruby on Rails 5.2.8.1

Since v5.2.8.1

Available in: v5.2.8.1 v6.0.6 v6.1.7.10 v7.0.10 v7.1.6 v7.2.3 v8.0.4 v8.1.2

Compare with:

See dev.mysql.com/doc/refman/5.7/en/error-messages-server.html