2

我有两个表：“系列”和“产品”

“系列”包含系列书籍的名称，“产品”包含个别书籍名称的详细信息。

所以是这样的：

Series Table:
id      series_name               series_description
1       Lord of the Rings         Trilogy of fantasy books recently made into film
2       A Song of Ice and Fire    Epic series of novels currently showing on HBO
3       Harry Potter              Famous Children's book series also loved by adults

Product Table:
id      product_name              series_id     author             etc...
1       Fellowship of the Ring    1             JRR Tolkien
2       The Two Towers            1             JRR Tolkien
3       Return of the King        1             JRR Tolkien
4       A Game of Thrones         2             George R R Martin
5       A Clash of Kings          2             George R R Martin
6       A Storm of Swords         2             George R R Martin
7       A Feast for Crows         2             George R R Martin
8       A Dance with Dragons      2             George R R Martin
9       Harry Potter and the...   3             JK Rowling
etc.

我想 SELECT * FROM series 和 COUNT(*) FROM product 以便查询返回一个包含系列信息的表，数据库中与每个系列对应的产品数量附加为表的最后一列。我也想按类型来做，所以在某处有一个额外的 WHERE 子句。如果选择“幻想与魔法”作为类型，它看起来像这样：

id      series_name               series_description         number_of_products
1       Lord of the Rings         Trilogy of Fantasy...      3
2       A Song of Ice and Fire    Epic Series of Novels...   5
3       Harry Potter              Famous Children's book...  7

我想我可能需要 LEFT JOIN，但到目前为止我的最佳尝试一直在进行。

这是我到目前为止所拥有的，但我认为这可能是完全错误的。

SELECT  series.id,                                   
series.series_name,                                         
series.publisher_id,                                       
series.description, 
series.image, 
COUNT (product.*) as nRows 
FROM series 
LEFT OUTER JOIN product
ON series.id = product.series_id                    
WHERE series.genre = 'Fantasy and Magic'
GROUP BY ... (do I need a GROUP BY?)

任何帮助都将不胜感激。提前致谢！

4

2 回答 2

7

差不多好了。尝试这个。

SELECT  series.id,                                   
series.series_name,                                         
series.publisher_id,                                       
series.description, 
series.image, 
COUNT (product.id) as nRows 
FROM series 
LEFT OUTER JOIN product
ON series.id = product.series_id                    
WHERE series.genre = 'Fantasy and Magic'
GROUP BY series.id,                                   
series.series_name,                                         
series.publisher_id,                                       
series.description, 
series.image
于 2013-02-01T09:05:30.260 回答
0

这不是有帮助吗？

select s.id, 
   s.series_name, 
   s.series_description, 
   (select count(*) from Products p where p.series_id = s.id) number_of_products 
from Series s
于 2013-02-01T09:08:46.297 回答