mysql-按不存在的值分组

是否可以按“不存在”分组（如果这不是正确的术语，请抱歉）

例如，如果我有一个表，例如：

post_id-状态

1-主动

2-暂停

3-暂停

状态表的可能值为：活动、暂停、保持、删除

但是status列在任何给定时间都可能有或可能没有所有这些状态类型，但是我仍然希望返回一个计数为0的状态，即使它不在其中

是否可以执行以下操作（伪查询）：

按状态从用户组中选择计数（post_id）、状态（活动、暂停、保留、删除）

---

注意：在任何人建议不这样做之前，我没有选择，因为这是这个CMS的属性表的结构。

Try

case

语句

SELECT SUM(CASE WHEN status = "active" THEN 1 ELSE 0 END) active_count,
       SUM(CASE WHEN status = "suspended" THEN 1 ELSE 0 END) suspended_count,
       SUM(CASE WHEN status = "hold" THEN 1 ELSE 0 END) hold_count,
       SUM(CASE WHEN status = "deleted" THEN 1 ELSE 0 END) deleted_count
FROM posts;

还有这个

SELECT "active", SUM(CASE WHEN status = "active" THEN 1 ELSE 0 END) active_count
FROM posts
UNION
SELECT "suspended", SUM(CASE WHEN status = "suspended" THEN 1 ELSE 0 END) suspended_count
FROM posts
UNION
SELECT "hold", SUM(CASE WHEN status = "hold" THEN 1 ELSE 0 END) hold_count
FROM posts
UNION
SELECT "deleted", SUM(CASE WHEN status = "deleted" THEN 1 ELSE 0 END) deleted_count
FROM posts

更好

SELECT "active", COUNT(*) active_count
FROM posts WHERE status = "active"
UNION
SELECT "suspended", COUNT(*) suspended_count
FROM posts WHERE status = "suspended"
UNION
SELECT "hold", COUNT(*) hold_count
FROM posts WHERE status = "hold"
UNION
SELECT "deleted", COUNT(*) deleted_count
FROM posts WHERE status = "deleted"

---

请参阅SQL FIDLE

Try

case

语句

SELECT SUM(CASE WHEN status = "active" THEN 1 ELSE 0 END) active_count,
       SUM(CASE WHEN status = "suspended" THEN 1 ELSE 0 END) suspended_count,
       SUM(CASE WHEN status = "hold" THEN 1 ELSE 0 END) hold_count,
       SUM(CASE WHEN status = "deleted" THEN 1 ELSE 0 END) deleted_count
FROM posts;

还有这个

SELECT "active", SUM(CASE WHEN status = "active" THEN 1 ELSE 0 END) active_count
FROM posts
UNION
SELECT "suspended", SUM(CASE WHEN status = "suspended" THEN 1 ELSE 0 END) suspended_count
FROM posts
UNION
SELECT "hold", SUM(CASE WHEN status = "hold" THEN 1 ELSE 0 END) hold_count
FROM posts
UNION
SELECT "deleted", SUM(CASE WHEN status = "deleted" THEN 1 ELSE 0 END) deleted_count
FROM posts

更好

SELECT "active", COUNT(*) active_count
FROM posts WHERE status = "active"
UNION
SELECT "suspended", COUNT(*) suspended_count
FROM posts WHERE status = "suspended"
UNION
SELECT "hold", COUNT(*) hold_count
FROM posts WHERE status = "hold"
UNION
SELECT "deleted", COUNT(*) deleted_count
FROM posts WHERE status = "deleted"

---

请参见SQL fiddle，我的查询与Oracle相同。下面我们来做这项工作

select * from (
  select status from users
)
pivot (
  count(status) as count
  for status in ('active' as A, 'suspended' as S, 'hold' as H, 'deleted' as D)
);

---

信用证：

我的查询与Oracle相同。下面我们来做这项工作

select * from (
  select status from users
)
pivot (
  count(status) as count
  for status in ('active' as A, 'suspended' as S, 'hold' as H, 'deleted' as D)
);

---

积分：

您可以使用合成数据对查询结果进行连接。例如，

选择coalesce（r.count，0）作为count，s.status from statuses as s left join{that query}作为r on s.status=r.status

，其中statuses包含分组的已知状态集。我该怎么做？你能用几行样本数据和所需的输出来说明你的问题吗。也许只是我，但我很难理解你真正想要的是什么。同上@peterm，abd为什么你要从用户表中选择？当然，这将是posts表。是否要按用户分组？请详细说明。不管表名是什么，这是一个包含简单数据的假表，用于简化问题，并使用合成数据连接查询结果。例如，

选择coalesce（r.count，0）作为count，s.status from statuses as s left join{that query}作为r on s.status=r.status

，其中statuses包含分组的已知状态集。我该怎么做？你能用几行样本数据和所需的输出来说明你的问题吗。也许只是我，但我很难理解你真正想要的是什么。同上@peterm，abd为什么你要从用户表中选择？当然，这将是posts表。是否要按用户分组？请详细说明。不管表名是什么，这是一个带有简单数据的假表，以简化问题