Apparently you can pash a second scope to a hash-condition and the whole thing will be evaluated as a second SELECT statement with a subselect.

Rails Long Term Support

Rails LTS provides security patches for old versions of Ruby on Rails (2.3, 3.2, 4.2 and 5.2)

• Prevents you from data breaches and liability risks
• Upgrade at your own pace
• Works with modern Rubies

Read more Show archive.org snapshot

Note that sub-queries are extremely slow in MySQL, but they can make cases easier where performance does not matter so much (e.g. a migration on 50K records).