sql - 在 CASE SQL 语句中使用 BETWEEN

Question

我想从我们的费率表中获取所有 12 个月的平均费率并将其除以月份，我开始编写带有大小写的 SQL select，但我似乎在“Between”部分中做错了一些事情......这里是我的 SQL

SELECT AVG(SELL_RATE),
       AVG(BUY_RATE),
       CASE MONTHS
            WHEN RATE_DATE( BETWEEN '2010-01-01' AND '2010-01-31') THEN 'JANUARY'
            ELSE 'NOTHING'
   END AS 'MONTHS'
FROM   RATE
WHERE  CURRENCY_ID = CURRENCY -033'

Answer 1

从你的案例中取出月份，然后去掉括号......像这样:

CASE 
    WHEN RATE_DATE BETWEEN '2010-01-01' AND '2010-01-31' THEN 'JANUARY'
    ELSE 'NOTHING'
END AS 'MONTHS'

您可以将其视为等同于:

CASE TRUE
    WHEN RATE_DATE BETWEEN '2010-01-01' AND '2010-01-31' THEN 'JANUARY'
    ELSE 'NOTHING'
END AS 'MONTHS'