mysql - 如何在 WHERE 子句中使用别名列 day？

Question

我有一个关于这个查询的问题:

  SELECT DAYOFYEAR(t.ts_start) AS 'day', YEAR(t.ts_start) AS year, t.o AS value FROM Cryptoforecast_ETH_BTC_1h AS t 

当我运行它时，它会显示结果。现在我想过滤一天，添加这样的 WHERE 语句

SELECT DAYOFYEAR(t.ts_start) AS 'day', YEAR(t.ts_start) AS year, t.o AS value FROM Cryptoforecast_ETH_BTC_1h AS t WHERE 'day'=157

但是没有结果和警告:

Truncated incorrect DOUBLE value: 'day'

问题是什么？

Answer 1

只需在 WHERE 子句中重复调用 DAYOFYEAR:

SELECT
    DAYOFYEAR(t.ts_start) AS day,
    YEAR(t.ts_start) AS year,
    o AS value
FROM Cryptoforecast_ETH_BTC_1h
WHERE DAYOFYEAR(t.ts_start) = 157;

或者，如果您想使用 day 别名，您可以使用重载的 HAVING 子句:

SELECT
    DAYOFYEAR(t.ts_start) AS day,
    YEAR(t.ts_start) AS year,
    o AS value
FROM Cryptoforecast_ETH_BTC_1h
HAVING day = 157;