Mysql 如何在WHERE子句中使用别名列day？

我对这个问题有一个疑问：

  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。现在我想过滤一天中添加的

WHERE

语句，如下所示

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

但这并没有带来任何结果和警告：

Truncated incorrect DOUBLE value: 'day'

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问题是什么？

您不能在

WHERE

子句中使用别名列。所以，实际上并不是比较列，而是比较字符串值和int

WHERE 'day'=157

相反，你可以使用

WHERE DAYOFYEAR(t.ts_start) = 157

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旁注：您不需要对列别名使用单引号。

只需重复调用

WHERE

子句中的

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;

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

或者，如果您想使用

day

别名，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
WHERE DAYOFYEAR(t.ts_start) = 157;

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

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尝试此操作，

选择DAYOFYEAR（t.ts_start）作为day，选择YEAR（t.ts_start）作为YEAR，选择t.o作为Cryptoforecast的值，选择t.o作为t HAVING day=157