Question

我有一个具有以下值的数据表“ BondPrices”：

date     | type | price  
1/5/2019   bid    104.50  
1/5/2019   bid    104.75
1/6/2019   bid    104.40  
1/6/2019   bid    104.45   
1/5/2019   offer  106.75   
1/5/2019   offer  107.75
1/6/2019   offer  106.23
1/6/2019   offer  106.47

我想编写一个查询，给出给定日期的最高出价和最低价格，例如以下输出：

date     | Highest Bid | Lowest Offer
1/5/2019   104.75        106.75
1/6/2019   104.45        106.23

这样做可以达到最高出价或最低出价

SELECT "date", max("price") AS "Highest Bid"
FROM "BondPrices" 
WHERE "type"='bid' 
GROUP BY "date"

或

SELECT "date", min("price") AS "Lowest Offer"
FROM "BondPrices" 
WHERE "type"='offer' 
GROUP BY "date"

但是当我尝试将它们结合在一起（例如与JOIN结合使用）时，会出现语法错误。

如何编写具有多个条件并导致多个列的select语句？

Answer 1

有几种方法可以在这里给猫皮，这将带您到那里：

SELECT
    CAST(date AS DATE) Date,
    MAX(CASE WHEN type = 'bid' THEN price ELSE NULL END) HighestBid,
    MIN(CASE WHEN type = 'offer' THEN price ELSE NULL END) LowestOffer
FROM 
    BondPrices
GROUP BY 
    CAST(date AS DATE)

SQL多条件选择

1 个答案: