Recently, at eet.nu we have been working on migrating a Ruby on Rails application from MySQL to PostgreSQL. Depending on the complexity of an app, there might be many caveats during migration. Here are some notes on issues that we solved during the migration. This article assumes that we work with: Ruby on Rails 4; MySQL 5.6; PostgreSQL 9.4. Quoting and Boolean fields MySQL uses backticks (`) for quoting, while in PostgreSQL double quotes (") are being used. MySQL uses TINYINT datatype to represent boolean fields. Therefore, 1 would represent true and 0 would represent false. PostgreSQL has native boolean datatype.