Use a variable for your query, for example strSQLquery.
Before your execute query activity, assign strSQLquery = “select " + variable + " * from booking.dbo.booking”
I’m not familiar with SQL but have worked with SOQL. I have just copied your query code.
Make sure that you do not have extra spaces in your "variable’ as you already have one after “select” and before “*”. You can also try using & instead of +, like:
strSQLquery = “select " & variable.trim & " * from booking.dbo.booking”