Q:

Can we write queries in Multichain like select * from Stream1.key1 where key1.value = “xyz”

Can we write queries in Multichain to retrieve conditional data from streams e.g. select * from  Stream1.key1 where key1.value = “xyz”

A:

You have many different ways of slicing and dicing stream items, but it does not support SQL. I'm not sure what you want to do with this query, but maybe liststreamkeyitems is what you're looking for? See the 'Querying subscribed streams' section on this page:
https://www.multichain.com/developers/json-rpc-api/

