计数来自2个表的查询

Question

我有2张这样的桌子。 对于给定的属性（在表doc_attribute中）和文件中的给定“字”（在文档中），我想查找不包含该特定属性但在文件中包含该“字”的不同doc_id的计数。

例如，如果给定的属性是camera并且'word'是mobile，则结果应为2。（即，第2、3和5 doc_id不包含camera，并且其中只有2nd和3rd包含'word'mobile）文件）

table doc_attribute
+--------+-----------+--------+
| doc_id | attribute | value  |
+--------+-----------+--------+
|     1 | product   | mobile |
|     1 | model     | lumia  |
|     1 | camera    | 5mp    |
|     2 | product   | mobile |
|     2 | model     | lumia  |
|     2 | ram       | 1gb    |
|     3 | product   | mobile |
|     3 | year      | 2014   |
|     3 | made-in   | china  |
|     4 | brand     | apple  |
|     4 | model     | iphone |
|     4 | camera    | 5mp    |
|     5 | product   | camera |
|     5 | brand     | canon  |
|     5 | price     | 20000  |



  table document
  +--------+-----------------------------+
  | doc_id | file                        |
  +--------+-----------------------------+
  |     1 | lumia 5mp mobile 1gb   2014  |
  |     2 | lumia 8mp mobile 1gb   2015  |
  |     3 | galaxy mobile fullhd 2gb     |
  |     4 | iphone apple 5mp 2013 new    |
  |     5 | canon 20000 new dslr 12mp    |

当前查询：

select count(doc_id)
from document
where doc_id not in (select doc_id from doc_attribute
                     where attribute = 'camera')
  and file REGEXP '[[:<:]]mobile[[:>:]]';

Answer 1

使用正则表达式和左联接即可。

declare @attribute varchar(128), @word varchar(128)

SELECT @attribute='camera', @word='mobile'

SELECT count(DISTINCT document.id) Results
FROM document
LEFT JOIN doc_attribute
on document.id=doc_attribute.id AND doc_attribute.attribute=@attribute
WHERE doc_attribute.id IS NULL
AND file like '%'+@word+'%'