在MySql中對行進行計數和分組

Question

我使用Mysql數據庫版本5.5.24-log。

在此表中，我無法計算和分組字段Premium_name的值。

在輸出中，我需要2作為最終值，因為在表中只有兩個Premium_name：HYDROSPEED和GLOCKENSPIELMEMORIAL。

先感謝您。

SELECT
    COUNT(*), Premium_name
FROM
    `table_premium`
GROUP BY
    Premium_name;

+----------+----------------------+
| COUNT(*) | Premium_name         |
+----------+----------------------+
|        2 | GLOCKENSPIELMEMORIAL |
|        6 | HYDROSPEED           |
+----------+----------------------+
2 rows in set


+--------------+------------------+----------------------+--------------+
| Premium_area | Premium_sub_area | Premium_name         | Premium_code |
+--------------+------------------+----------------------+--------------+
| 51PD         | 51PDK1           | HYDROSPEED           |     48069794 |
| 51PD         | 51PDK1           | HYDROSPEED           |     48069795 |
| 51PD         | 51PDK1           | HYDROSPEED           |     49301672 |
| 51PD         | 51PDK1           | HYDROSPEED           |     52480075 |
| 51PD         | 51PDK1           | HYDROSPEED           |     52646404 |
| 51PD         | 51PDK1           | HYDROSPEED           |     91189540 |
| 51PD         | 51PDK2           | GLOCKENSPIELMEMORIAL |     45824206 |
| 51PD         | 51PDK2           | GLOCKENSPIELMEMORIAL |     48479834 |
+--------------+------------------+----------------------+--------------+

Answer 1

嘗試這個：

SELECT COUNT(1) AS PREMIUMS FROM
(SELECT
 DISTINCT Premium_name
 FROM
`table_premium`)CS

Answer 2

SELECT COUNT(DISTINCT Premium_name), Premium_name 
FROM
    `table_premium`

Answer 3

SELECT COUNT（DISTINCT Premium_name），Premium_name FROM table_premium組按Premium_name