Sql 计数中没有零值,按2个顺序排列
我有三张桌子:Sql 计数中没有零值,按2个顺序排列,sql,postgresql,cross-join,Sql,Postgresql,Cross Join,我有三张桌子: +---------+ +----------+ +----------+ | kkw | | block | | status | +---------+ +----------+ +----------+ | kkw_id | | block_id | |status_id | | land_id | | kkw_id | | .... | | ... | | statu
+---------+ +----------+ +----------+
| kkw | | block | | status |
+---------+ +----------+ +----------+
| kkw_id | | block_id | |status_id |
| land_id | | kkw_id | | .... |
| ... | | status_id| | .... |
+---------+ +----------+ +----------+
我想显示每个国家(land_id)和状态的块数,如果一个国家没有对应于状态的块,则为零。我尝试此请求,但未显示零值:
SELECT s.status_id, k.land_id, COUNT(b.block_id)
FROM kkw_status AS s
LEFT JOIN block AS b ON s.status_id = b.status_id
LEFT JOIN kkw AS k ON b.kkw_id=k.kkw_id
GROUP BY s.status_id, k.land_id
ORDER BY k.land_id, s.status_id;
结果:
status_id land_id count
1 1 2
4 1 3 ....
但我想:
status_id land_id count
1 1 2
2 1 0
3 1 0
4 1 3 .....
有什么想法吗?谢谢您正在按
k.land\u id
进行分组。因此,当某些内容不匹配时,该列的值为NULL
。因此,零值只会显示在这样的行上
如果需要所有状态id
s和land\u id
s,则使用交叉连接创建所有这些属性的列表,然后计算与每个组匹配的数量。我认为这就是查询的样子:
SELECT s.status_id, k.land_id, COUNT(b.block_id)
FROM kkw_status s CROSS JOIN
kkw k LEFT JOIN
block b
ON b.status_id = s.status_id AND b.kkw_id = k.kkw_id
GROUP BY s.status_id, k.land_id
ORDER BY k.land_id, s.status_id;
最有可能的情况是kkw_状态表中缺少值,因为在查询中没有进行筛选。就是这样!谢谢。