的MySQL如何顯示列和表

Question

我想要得到這樣的輸出的平均值爲：

Average score 
10 
col1 col2 score 
... 

使用

SELECT AVG(Score), * 
FROM (
SUM(...) AS col1 
SUM(...) AS col2 
SUM(...) AS Score 
) AS T1 

這是工作的時候我只選擇AVG（分數）或*，但不是都。有沒有什麼辦法可以在不重複代碼的情況下做到這一點？

這是我得到的錯誤，當我嘗試：

ERROR 1064 (42000) at line 27: You have an error in your SQL syntax; check 
the manual that corresponds to your MySQL server version for the right 
syntax to use near '* 
FROM (
SELECT 
    testresults.hostname AS Hostname, 
    hostinfo.env A' at line 3 

Answer 1

不能與其他列使用*。你可以這樣做：

SELECT * FROM... 

或

SELECT col1, col2, col3... FROM... 

但不

SELECT col1, col2, col3, * FROM... 

例如：

mysql> SELECT id FROM users LIMIT 5; 
+----+ 
| id | 
+----+ 
| 18 | 
| 22 | 
| 23 | 
| 26 | 
| 27 | 
+----+ 
5 rows in set (0.00 sec) 

mysql> SELECT id, * FROM users LIMIT 5; 
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '* FROM users LIMIT 5' at line 1 

Answer 2

你可以做這樣的事情：

SELECT * 
FROM 
test t, 
(SELECT AVG(score) AS average_score 
FROM test) a; 

這是SQL Fiddle。