Question

到目前为止，我有以下内容：

   SELECT D.department AS dept, C.name AS subdept
    FROM (SELECT DISTINCT department FROM classes WHERE web != 0 ORDER BY department,name LIMIT 5) D
    LEFT JOIN classes C ON (C.department = D.department)
    ORDER BY D.department,C.name

结果如下：

+------+-------------------------------+
| dept | subdept                       |
+------+-------------------------------+
| BOOK | CHILDRENS BOOKS               |
| BOOK | DVD'S                         |
| CLOT | ACCESSORIES                   |
| CLOT | APRONS                        |
| FEED | BIBS & BURP CLOTHS            |
| FEED | BOTTLE & FOOD WARMERS         |
+------+-------------------------------+

我想要获得的是每个部门的'标题'，其中包含一个空的子标题，例如：

+------+-------------------------------+
| dept | subdept                       |
+------+-------------------------------+
| BOOK | null                          |
| BOOK | CHILDRENS BOOKS               |
| BOOK | DVD'S                         |
| CLOT | null                          |    
| CLOT | ACCESSORIES                   |
| CLOT | APRONS                        |
| FEED | null                          |    
| FEED | BIBS & BURP CLOTHS            |
| FEED | BOTTLE & FOOD WARMERS         |
+------+-------------------------------+

表的结构：departments表具有作为外键的类department字段的id主键。

Departmens：id |名称（部门）课程：部门|名称（班级）

根据DanfromGermany向我展示的内容，我有：

SELECT D.department AS dept, C.name AS subdept
FROM
 (SELECT DISTINCT department FROM classes WHERE web != 0 ORDER BY department,name  LIMIT 5) D
LEFT JOIN classes C ON (C.department = D.department)
GROUP BY D.department, C.name WITH ROLLUP

现在给出：

+--------+-------------------------------+
| dept   | subdept                       |
+--------+-------------------------------+
| BOOK   | CHILDRENS BOOKS               |
| BOOK   | DVD'S                         |
| BOOK   | [NULL]                        |
| CLOT   | ACCESSORIES                   |
| CLOT   | APRONS                        |
| CLOT   | [NULL]                        |
| FEED   | BIBS & BURP CLOTHS            |
| FEED   | BOTTLE & FOOD WARMERS         |
| FEED   | [NULL]                        |
| GEAR   | BOOSTER CAR SEATS             |
| GEAR   | CAR SEAT ACCESSORIES          |
| GEAR   | [NULL]                        |
| GIFT   | BABY BASKETS & DIAPER CAKES   |
| GIFT   | BANKS                         |
| GIFT   | [NULL]                        |
| [NULL] | [NULL]                        |
+--------+-------------------------------+

确定上次修改：

它通过子查询来使用order by：

SELECT * FROM
(SELECT D.department AS dept, C.name AS subdept
FROM
 (SELECT DISTINCT department FROM classes WHERE web != 0 ORDER BY department,name  LIMIT 5) D
LEFT JOIN classes C ON (C.department = D.department)
GROUP BY D.department, C.name WITH ROLLUP
) T
ORDER BY dept,subdept

Answer 1

将您的查询更改为GROUP BY子句，然后使用WITH ROLLUP。

请参阅该页面中间： http://dev.mysql.com/doc/refman/5.1/en/group-by-modifiers.html

或谷歌搜索“GROUP BY WITH ROLLUP mysql”

像这样（未经测试）：

SELECT D.department AS dept, C.name AS subdept
FROM
 (SELECT DISTINCT department FROM classes WHERE web != 0 ORDER BY department,name  LIMIT 5) D
LEFT JOIN classes C ON (C.department = D.department)
GROUP BY dept, subdept WITH ROLLUP
ORDER BY D.department,C.name

mysql - 添加标题以跨连接查询

1 个答案: