mysql - JOIN 查询的行为不符合预期

Question

我正在处理一个未按预期运行的查询，如果您能帮助我指明正确的方向，我将不胜感激。

表格 我有三个中心表，由以下内容组成。

table_categories
- id (int)
- name (varchar)

table_events
- id (int)
- name (varchar)
- created (date time)

table_taxonomy
- cat_id (id from table_categories)
- event_id (id from table_events)
- type (varchar in this example always 'category')

目标 统计每个类别中特定日期之后创建的事件。结果应该类似于:

COUNT   NAME    ID
3       Rock     1
2       Punk     3 

查询 这是我提出的查询。问题是结果不关心创建日期，而是获取所有事件，无论它们何时创建。

SELECT COUNT(*) AS count,
            table_categories.name,
            table_categories.id
            FROM table_taxonomy
            INNER JOIN table_categories
            ON table_categories.id = table_taxonomy.cat_id
            LEFT JOIN table_events
            ON table_events.id = table_taxonomy.events_id
            WHERE table_taxonomy.type = 'category'
            AND table_taxonomy.cat_id IN(2,3)
            AND table_events.created > '2012-10-07 05:30:00'
            GROUP BY (table_categories.name)

Answer 1

试试这个，在比较日期时只需做一些小小的改变:

SELECT COUNT(*) AS count,
            table_categories.name,
            table_categories.id
            FROM table_taxonomy
            INNER JOIN table_categories
            ON table_categories.id = table_taxonomy.cat_id
            LEFT JOIN table_events
            ON table_events.id = table_taxonomy.events_id
            WHERE table_taxonomy.type = 'category'
            AND table_taxonomy.cat_id IN(2,3)
            AND Date(table_events.created) > '2012-10-07 05:30:00'
            GROUP BY (table_categories.name)