函数错误book.Description不存在

Question

我正试着走到这张桌子上：

+-------------------------------------------+------------+------------------------+
| Title                                     | Avg Rating | Description Excerpt    |
+-------------------------------------------+------------+------------------------+
| The Shortest Book in the World            | 10         | A Guide to how Detro...|
| From Deep in the Heart of Texas to IT     | 6          | One man's Journey to...|
| From the Shores of Lake Erie to IT        | 4          | One man's Journey to...|
| The Science of Literature Searching       | NULL       | A Book Worth a Look ...|
| Master Wireless Through The Classic Comics| NULL       | Infrared man triumph...|
| Master HTML Through The Classic Comics    | NULL       | Using his Super Web ...|
| Master C++ Through The Classic Comics     | NULL       | GeekMan triumphs ove...|
+-------------------------------------------+------------+------------------------+
7 rows in set (0.00 sec)

+-------------+--------------+------+-----+---------+-------+
| Field       | Type         | Null | Key | Default | Extra |
+-------------+--------------+------+-----+---------+-------+
| ISBN        | char(13)     | NO   | PRI |         |       |
| Title       | varchar(70)  | NO   |     | NULL    |       |
| Description | varchar(100) | YES  |     | NULL    |       |
| Category    | int(11)      | YES  | MUL | NULL    |       |
| Edition     | char(30)     | YES  |     | NULL    |       |
| PublisherID | int(11)      | NO   | MUL | NULL    |       |
+-------------+--------------+------+-----+---------+-------+
6 rows in set (0.00 sec)


select b.title as "Title", round(avg(br.rating)) as "Avg Rating", 
CONCAT(Description(1, 20, '...')) as "Description Excerpt" 
from  (book b LEFT JOIN bookreview br on b.ISBN = br.ISBN) 
order by  upper(b.title);  

--------------
select b.title as "Title", round(avg(br.rating)) as "Avg Rating",
CONCAT(Description(1, 20, '...')) as "Description Excerpt"
 from  (book b LEFT JOIN bookreview br on b.ISBN = br.ISBN)
 order by  upper(b.title)
 --------------

错误1305 (42000)：函数book.Description不存在

我对这个错误感到困惑，但是当我对我的图书表运行desc时，带有描述的图书表马上就会显示出来。我需要帮助来弄清楚这个问题。

Answer 1

我认为您需要一个带有连接的SUBSTR函数，因此，请更改

CONCAT(Description(1, 20, '...'))

至

CONCAT(substr(Description ,1, 20), '...')