如何计算值（重复项除外）？

Question

如何计算列中的值（重复项除外）。我尝试这个代码，但我没有。感谢您的帮助。 （对不起我的英文不好）

long net = DatabaseUtils.longForQuery(db, "select date, count(*) from mytable GROUP BY date", null); 
nettext.setText(String.valueOf(net));  

For example: 
+----+------------+ 
| id | date  | 
+----+------------+ 
| 1 | 2006-10-08 | 
| 2 | 2006-10-08 | 
| 3 | 2006-10-09 | 
+----+------------+ 

There is two different date (2006-10-08 and 2006-10-09) 
Result must be = 2 

Answer 1

我找到了解决这一等。谢谢m.aibin。

long net = DatabaseUtils.longForQuery(db, "select count(DISTINCT date) from mytable", null); 

Answer 2

这应该工作：

long net = DatabaseUtils.longForQuery(db, "select count(DISTINCT date) from mytable GROUP BY date", null);