Question

假设我有一个名为process_states的表：

+--------+--------+
|Process | State  |
-------------------
|   A    |   0    |
|   A    |   0    |
|   B    |   0    |
|   B    |  -1    |
|   C    |  -99   |
-------------------
Note: State can have many more negative and positive state values

我想找到所有行状态为0的进程。在上面的例子中，我想得到A。

我试图使用group by来做，有没有办法做这样的事情：

select process from process_states 
group by process 
having <all state for that process is 0>

可以使用group by吗？

Answer 1

您可以使用group by子句并使用having子句过滤进程：

SELECT   process
FROM     process_states
GROUP BY process
HAVING   COUNT(CASE state WHEN -1 THEN 1 END) = 0

编辑：

鉴于对其他答案的澄清评论，如果要求仅查找仅具有0个状态的进程，则可以计算总行数和具有0状态的行数并比较它们：

SELECT   process
FROM     process_states
GROUP BY process
HAVING   COUNT(CASE state WHEN 0 THEN 1 END) = COUNT(*)

Answer 2

您可以group by处理列并检查状态列的最大值和最小值是否为0。

select process 
from process_states
group by process
having max(state) = min(state) and min(state) = 0

Answer 3

您可以使用having子句来完成此操作。如果给定进程的行数等于具有零的行数，则表示该进程只有零行。

select process
  from process_states
 group by process
 having count(*) = count(case when state = 0 then 'X' end)

Answer 4

我很想将min用于此：

select process
from process_status
group by process
having min(status) > -1;

这确实假设没有其他负面状态。

Answer 5

试试这个

select process
from process_status
group by process
having sum(abs(status))  = 0

基于其他列值的查询分组

5 个答案: