SQL query to find the sum of fields in a column if a condition matches else return a default value

Question

I need a SQL query for the below scenario

House| SquareFoot| Color

---

House1  10        White
House2  20        White

The query should give a sum of SquareFoot(30) only if all the values in Color field are the same. Else it should return (0) for the below scenario

House| SquareFoot| Color

---

House1  10        White
House2  20        Red

Please let me know the best way this can be achieved through SQL

Answer 1

You seem to want:

SELECT (CASE WHEN MIN(Color) = MAX(Color)
             THEN SUM(SquareFoot)
             ELSE 0
        END) as return_value
FROM t;

Answer 2

在这里，首先我们将从计数中检查是否非重复值= 1，然后总计将为sum（SquareFoot），或者如果非重复计数不为= 1，则总计将为0

select iif((select COUNT(distinct(Color)) from tblName) = 1, sum(SquareFoot), 0) as Total from tblName