Create UPDATE query examples

[jdegoes]

We need a few examples of UPDATE queries under different schemas, both to validate the design and flesh out edge cases, as well as to show people how to use the data type to model UPDATE queries.

[marcinkrykowski]

I'm not sure if this one still needs to be done or we can close it as mentioned here? @jczuchnowski @jdegoes @robmwalsh

[bertlebee]

That one was closed and split into new issues (with this being one of them)

[bertlebee]

@marcinkrykowski I think we've only got one example with one schema so we still need some more. Feel free to try and break the DSL and raise new issues - this is how we can make it better.