As the definaton of Datawarehouse say it is repository of historial data which is used by Busines users to run some reports on his/her area of interests.

Data is not loaded everyhour or every mtes in Data warehouse. so cannot be used as transaction. But it will reflect the data what is present in source system so in therory if you want to run any query in live(transaction database( , it will just slow down the transaction database so instead of that you can run the same query in DWH which faster and gives the result quicker.

Also data can be changed and modified in Datawarehouse. Data is loaded into a data warehouse on dail basis by ETL(extract , transform and load) process.

If you can tell us what exactly you want to do with Data warehouse database , can i can help you. I think data in data warehouse is very near to what is present in transaction data but in different form.