Here is my table:
Account (AccountId, UserId, Currency)
1 1 USD
2 1 USD
3 2 EUR
4 1 USD
5 2 USD
I need to compare the currencies because 1 user must only have 1 currency.
So, in my example, User1 currency is USD (no problem) so I can return the currency of User1.
But User2 has 2 currencies so I need to throw an error.
Thanks in advance for your help.