如何在 SQL QUERY (OPERA) 中只获取月份和年份

How to get only month & year in SQL QUERY (OPERA)

select ST.dateOfSale, ST.agreedPrice - C.purchasedPrice AS PROFIT
FROM SalesTransaction ST, Car C
WHERE ST.VIN = C.VIN
GROUP BY (ST.dateOfSale, (ST.agreedPrice - C.purchasedPrice))
ORDER BY ST.dateOfSale DESC ;

对于2020年的每个月,我只需要显示汽车销售产生的总利润

请参阅下面的table:

汽车(VIN、获取日期、制造年份、购买价格、要价)

销售交易(VIN、custID、agentID、dateOfSale、同意的价格)

好的做法 - 使用 JOIN 连接多个表

SELECT to_char(ST.dateOfSale,'YYYY'),to_char(ST.dateOfSale, 'mm'),SUM( ST.agreedPrice - C.purchasedPrice) AS PROFIT
FROM SalesTransaction ST, Car C
WHERE ST.VIN = C.VIN
GROUP BY to_char(ST.dateOfSale,'YYYY'),to_char(ST.dateOfSale, 'mm');