UNION is working exactly as intended. UNION doesn't add columns to a dataset, it adds further rows.

Without knowing your data this is a guess, but perhaps...

I assume it's running from some kind of Agent task? Could you set up a parameter instead, say CurrentDayNum. In the job you can set the value of the parameter...

When SSRS passes a set a values, it doesn't use an array. Arrays don't exist in SQL Server. Values for Multiple Values Parameters are passed as a delimited string. So,...

Unfortunately there seems to be language barrier here, but I don't understand what your question is.

You firstly seem to be saying you have a SQL Agent job that...

When you say you want to change the check, what do you mean exactly? Will the value of the @DayNum need to be a different value to evaluate to TRUE,...

Is it just for a specific subscription, or all of them? We have it set up on Exchange so that all emails sent our SSRS service account have specific text...

What would your NULL value represent? If you are supplying a list of items, what would you expect a list of no items to return?

I ask as, for...