bug fixed for exercises

data/2.MySQL中阶/4.聚合和分组/2. 求和/sum.md

@@ -47,5 +47,5 @@ select sum(total) from orders group by deal having unit_price > 1000;
 ### C
 
 ```sql
-select sum(total) from orders having deal and unit_price > 1000;
+select sum(total) from orders order by deal and unit_price > 1000;
 ```
\ No newline at end of file