问题

以下是翻译好的内容：

我有一个数据集，其原始值是整数。

SQL 查询很简单：

SELECT last("DischargingBattery") FROM battery

我想将非零数值转换为 "BUSY" 字符串，将零数值转换为 "IDLE"。SQL 查询应该类似于以下内容：

SELECT last("DischargingBattery"),

    CASE
        WHEN last("DischargingBattery") = 0 THEN 'IDLE'
        ELSE 'BUSY'
    END AS DischargingBatteryStatus

FROM battery

然而，我尚未在文档中找到相关参考资料。

是否有任何解决方法？

SELECT last("DischargingBattery") FROM battery

SELECT last("DischargingBattery") ,

    CASE
        WHEN last("DischargingBattery") = 0 THEN 'IDLE'
        ELSE 'BUSY'
    END AS DischargingBatteryStatus

FROM battery

答案1

得分: 1

I can not find any reference to case in any CnosDB docs either, so I'm drawn to the conclusion that it isn't (currently?) supported.

Also there does not seem to be "if" or "iif" with the select clause either.

So, in your case all I can suggest as an alternative is (but I dislike it):

SELECT
      0      as DischargingBattery
    , 'IDLE' AS DischargingBatteryStatus
FROM battery
WHERE last("DischargingBattery") = 0

UNION ALL

SELECT
      last("DischargingBattery")
    , 'BUSY' DischargingBatteryStatus
FROM battery
WHERE last("DischargingBattery") <> 0

NB: I am not familiar with the function `last`


<details>
<summary>英文:</summary>

I can not find any reference to `case` in any CnosDB docs either, so I&#39;m drawn to the conclusion that it isn&#39;t (currently?) supported.

Also there does not seem to be &quot;if&quot; of &quot;iif&quot; with the select clause either.

So, in your case all I can suggest as an alternative is (but I dislike it):


    SELECT
          0      as DischargingBattery
        , &#39;IDLE&#39; AS DischargingBatteryStatus
    FROM battery
    WHERE last(&quot;DischargingBattery&quot;) = 0
    
    UNION ALL
    
    SELECT
          last(&quot;DischargingBattery&quot;)
        , &#39;BUSY&#39; DischargingBatteryStatus
    FROM battery
    WHERE last(&quot;DischargingBattery&quot;) &lt;&gt; 0

NB: I am not familiar with the function `last`

</details>