我正在使用标签系统,它应该做的是您可以查询并选择标签,例如jQuery和javascript,库标签.它仅应显示与查询相关的脚本,并且仅显示具有标签的脚本.这是数据库布局：

脚本表：

+-----------+---------------+
| script_id | name          |
+-----------+---------------+
|         1 | jQuery        |
|         2 | Sencha Touch  |
|         3 | Codeigniter   |
|         4 | Google Chrome |
|         5 | memcached     |
|         6 | PHP           |
|         7 | MooTools      |
|         8 | node.js       |
|         9 | jQuery Mobile |
+-----------+---------------+

标签表：

+--------+-------------+-------------+
| tag_id | name        | url_name    |
+--------+-------------+-------------+
|      1 | JavaScript  | javascript  |
|      2 | Library     | library     |
|      3 | PHP         | php         |
|      4 | MySQL       | mysql       |
|      5 | Cache       | cache       |
|      6 | HTML        | html        |
|      7 | Open source | open-source |
+--------+-------------+-------------+

标记表：

+-----------+--------+-----------+
| tagged_id | tag_id | script_id |
+-----------+--------+-----------+
|         1 |      1 |         1 |  # javascript -- jQuery
|         2 |      2 |         1 |  # library    -- jQuery
|         3 |      1 |         9 |  # javascript -- jQuery mobile
+-----------+--------+-----------+

当我运行SQL时,它仍会选择jQuery Mobile,但不应这样做,因为它不包含jQuery所包含的库标签,我需要它来约束必须满足所选标签的结果.

这是我的SQL：

SELECT scripts.script_id,
       scripts.name
FROM
(
    scripts scripts

    LEFT OUTER JOIN tagged tagged ON tagged.script_id = scripts.script_id

    LEFT OUTER JOIN tags tags ON tags.tag_id = tagged.tag_id
)
WHERE MATCH(scripts.name) AGAINST ('jquery*' IN BOOLEAN MODE) AND ( tags.url_name = 'javascript' OR tags.url_name = 'library' )
GROUP BY script_id
ORDER BY scripts.name
LIMIT 0, 25

它返回：

+-----------+---------------+
| script_id | name          |
+-----------+---------------+
|         1 | jQuery        |
|         9 | jQuery Mobile |
+-----------+---------------+

如果将OR更改为AND,则根本不会返回任何内容,或者如果我从标签(和)中删除了括号,也不会返回任何内容.

如何使查询约束标签？

解决方法:

试试看：

select s.script_id, s.name from scripts s
join tagged tj on s.script_id = tj.script_id
join tags t on t.tag_id = tj.tag_id
where s.name like 'jQuery%' and t.url_name in ('javascript', 'library')
group by s.script_id, s.name
having count(*) = 2
order by s.name
limit 25

唯一需要考虑的是,必须将2替换为in子句中的元素数量.

这是fiddle.