Output of adding an integer and a String in SQL Server

Question

I was asked what the following simple query would return.

Select 5 + '4'

As, 4 is string type, I expect the query to throw an error. I found I was wrong, tested it, and the result was 9. How does it return the sum?

Answer 1

If you mix data types such as INT and VARCHAR, SQL Server will always attempt to convert everything to the one that has the highest precedence.