Question

我正在运行mariaDB版本的mysql，查询结果如下

select count(*) as 'Non-HT Computes', vcpus_used as 'Status'
from compute_nodes
WHERE deleted_at is NULL
  AND hypervisor_hostname LIKE '%sriov%'
  AND vcpus < '21'
GROUP BY vcpus_used

+-----------------+--------+
| Non-HT Computes | Status |
+-----------------+--------+
|              20 |      0 |
|               5 |     16 |
+-----------------+--------+

这是我要尝试的操作，如果在Status列中值为0然后打印Available，并且如果值在16到20之间值In-used，如何即时更改返回值的结果？

最终结果应类似于

+-----------------+----------------+
| Non-HT Computes |      Status    |
+-----------------+----------------+
|              20 |     Available  |
|               5 |     In-Used    |
+-----------------+----------------+

我尝试过CASE语句，但是不确定如何将其与别名Status列放在一起，因为Status是伪列。

编辑：

我已经走了这么远，但无法找出如何打印Non-HT Computes表格：（

select CASE WHEN Status = 0 THEN 'available' ELSE 'In-used' END AS Status from (select count(*) as 'Non-HT Computes',vcpus_used as 'Status' from compute_nodes WHERE deleted_at is NULL AND hypervisor_hostname LIKE '%sriov%' AND vcpus < '21' GROUP BY vcpus_used) as a
+-----------+
| Status    |
+-----------+
| available |
| In-used   |
+-----------+

Answer 1

这可以完成工作。如果要在非零情况后进行限制，则可以使用having语句。

SELECT count(*) AS 'Non-HT Computes',
       CASE
           WHEN vcpus_used BETWEEN 16 AND 20 THEN "In-used"
           WHEN vcpus_used = 0 THEN "Available"
           ELSE "Non-Zero"
           END AS Status
FROM compute_nodes
WHERE deleted_at IS NULL
  AND hypervisor_hostname LIKE '%sriov%'
  AND vcpus < '21'
GROUP BY vcpus_used;

Answer 2

第一种选择是使用CASE：

SELECT count(*) AS 'Non-HT Computes',
       CASE
           WHEN vcpus_used = 0 THEN 'Available'
           WHEN vcpus_used >= 16 AND vcpus_used <= 20 THEN 'In-use'
       END  AS 'Status'
FROM compute_nodes
WHERE deleted_at IS NULL
  AND hypervisor_hostname LIKE '%sriov%'
  AND vcpus < '21'
GROUP BY vcpus_used

第二个选项是创建一个表，该表具有状态值（0、16、20）并针对该表进行联接。

CREATE TABLE status_text (
    id INT PRIMARY KEY,
    descr VARCHAR(32)
);

INSERT INTO status_text VALUES (0,'Available');
INSERT INTO status_text VALUES (16,'In-use');
INSERT INTO status_text VALUES (20,'In-use');

SELECT count(*) AS 'Non-HT Computes',descr AS status
FROM compute_nodes
JOIN status_text ON (id=vcpus_used) 
WHERE deleted_at IS NULL
  AND hypervisor_hostname LIKE '%sriov%'
  AND vcpus < '21'
GROUP BY vcpus_used

MySQL根据条件更改查询结果

2 个答案: