Once you know that you are working with a subset of SQL you figure out what is NOT supported. You make a list of those things and distribute that list. Soon you come up with a list of "SHALL NOT"s for your developers and you put them up as posters.
Next you test everything. Over, and over, and over. You hand the device to your six year old who had a bad day at school and say, "have fun". You go insult your testing staff, turn off their air conditioning, and tell them how proud the developers are of the new release candidate. My wife is blind, we hand her a device and she pokes things at random.
Now that you know the testing environment you design with a small memory foot print in mind. "In order to perform this function what is the least amout of data that is required?" We are so used to SQL handling thousands of transactions per second it takes a new mind set to adjust to a version of SQL that only handles a few hundred transactions per minute. Don't think of the device as a small computer but, rather, an advanced calculator.
It's all mind set. On the device you are single user, not multi-user. In a traditional app we are always aware that the contents of the tables are ever changing. If I'm not live (working on local database and then sync.) then there is no one else changing my data. If I asked a question I remember the result and don't keep asking the same question over again.
Solid design starts with "paper testing". Chart and diagram your processes. Then KISS. Keep It So Simple. It's not your code that will impress the customer. It's how fast your app is out in the field.
By the way its fun taking a sales order on a device that looks like a side arm for the Borg. "Mr deli manager are you sure you only want two cases of this product that's on special?" Then you point right at his chest and pull the trigger a couple of times. Watch his expression as he sees the beam across his heart. "Six cases did you say? According to the database you get a quantity discount starting at eight cases." Click click. "An even dozen then? Very well."