```ruby
::Sequel.migration do
  up do
    fetch('UPDATE aliquots SET quantity = quantity*1000 WHERE quantity is not null AND `type` = "solvent"').all
  end

  down do
    fetch('UPDATE aliquots SET quantity = quantity/1000 WHERE quantity is not null AND `type` = "solvent"').all
  end
end
```

Fix migration. Use Sequel instead of plain SQL
user
```ruby
::Sequel.migration do
  up do
    self[:aliquots].exclude(:quantity => nil).where(:type => "solvent").update(:quantity => Sequel.expr(:quantity) * 1000)
  end

  down do
    self[:aliquots].exclude(:quantity => nil).where(:type => "solvent").update(:quantity => Sequel.expr(:quantity) / 1000)
  end
end
```
assistant