如何在 MySql 中将 Query 设置为变量答案

【问题标题】：How to set Query into variable in MySql如何在 MySql 中将 Query 设置为变量
【发布时间】：2021-09-06 15:07:15
【问题描述】：

我想查找每个组中最便宜和最贵的商品的商品名称。但我不知道为什么我在“SET @maxi := (SELECT A.ItName FROM tblqtdtl B INNER JOIN tblitem A ON A.ItCode = B.ItCode GROUP BY A.ItCode HAVING MAX(B.Price))”附近有 SQL 错误 (1064)。也许我的 sql 代码有问题或遗漏了一些东西

这是我所期待的

vd code	vd name	cheapest item	cheapest price	Most expensive item	Most Expensive Price
Vd001	DEF Textile	Polyester	2600	Polyester	2600
Vd003	MNO Textile	Polyester	3228	Silk	3950
Vd004	XYZ Textile	Polyester	2800	Silk	3480

这是我的代码

SET @mini :=(SELECT A.ItName FROM tblqtdtl B INNER JOIN tblitem A ON A.ItCode = B.ItCode 
                    GROUP BY A.ItCode HAVING MIN(B.Price)
                )
SET @maxi := (SELECT A.ItName FROM tblqtdtl B INNER JOIN tblitem A ON A.ItCode = B.ItCode 
                    GROUP BY A.ItCode HAVING MAX(B.Price)
                 )

SELECT V.VdCode, V.VdName, @mini AS 'Cheapest Item', MIN(B.Price) AS 'Cheapest Price', @maxi AS 'Most Expensive Item'
,MAX(B.Price) AS 'Most Expensive Price'
 
 FROM tblqthdr C 
 INNER JOIN tblvendor V ON C.VdCode = V.VdCode
 INNER JOIN tblqtdtl B ON C.DocNo = B.DocNo
 INNER JOIN tblitem A ON B.ItCode = A.ItCode
 WHERE V.ActInd='Y'
 GROUP BY V.VdCode

这是输入脚本

tblqdtl

INSERT INTO `tblqtdtl` (`DocNo`, `ItCode`, `Price`) VALUES
    ('QT001', 'It004', 38700.00),
    ('QT002', 'It002', 25600.00),
    ('QT003', 'It005', 21000.00),
    ('QT004', 'It004', 34000.00),
    ('QT005', 'It003', 32000.00),
    ('QT006', 'It002', 31780.00),
    ('QT007', 'It001', 28000.00),
    ('QT008', 'It002', 21800.00),
    ('QT009', 'It004', 32600.00),
    ('QT010', 'It002', 27500.00);

tbitem

INSERT INTO `tblitem` (`ItCode`, `ItName`, `ItCtCode`) VALUES
    ('Itestt001', 'Cotton', 'ALA'),
    ('It002', 'Polyester', 'SIN'),
    ('It003', 'Wool', 'ALA'),
    ('It004', 'Silk', 'ALA'),
    ('It005', 'Rayon', 'SIN');

tblqhdr

INSERT INTO `tblqthdr` (`DocNo`, `DocDt`, `VdCode`) VALUES
    ('QT001', '20180102', 'Vd003'),
    ('QT002', '20180203', 'Vd001'),
    ('QT003', '20180203', 'Vd002'),
    ('QT004', '20180207', 'Vd004'),
    ('QT005', '20180304', 'Vd003'),
    ('QT006', '20180401', 'Vd003'),
    ('QT007', '20180701', 'Vd005'),
    ('QT008', '20180902', 'Vd002'),
    ('QT009', '20180902', 'Vd005'),
    ('QT010', '20181203', 'Vd004');

tblvendor

INSERT INTO `tblvendor` (`VdCode`, `VdName`, `ActInd`) VALUES
    ('Vd001', 'ABC Textile', 'Y'),
    ('Vd002', 'DEF Textile', 'N'),
    ('Vd003', 'GHI Textile', 'Y'),
    ('Vd004', 'JKL Textile', 'Y'),
    ('Vd005', 'MNO Textile', 'N');

【问题讨论】：

请分享您需要的示例数据和输出的创建表和插入脚本。
对不起，我会分享插入脚本
如果您提供您遇到的错误，它也会有所帮助。
HAVING MIN(B.Price) 没有任何意义。 HAVING 后面需要跟一个真/假条件表达式。你的意思是HAVING B.Price = MIN(B.Price)？
这是我的期望所需输出中的价格值与示例数据中的价格值不匹配。

标签： mysql sql subquery inner-join

【解决方案1】：

SELECT DISTINCT
       VdCode,
       VdName,
       FIRST_VALUE(ItName) OVER (PARTITION BY VdCode ORDER BY Price ASC) `Cheapest item`,
       MIN(Price) OVER (PARTITION BY VdCode) `Cheapest price`,
       FIRST_VALUE(ItName) OVER (PARTITION BY VdCode ORDER BY Price DESC) `Most expensive item`,
       MAX(Price) OVER (PARTITION BY VdCode) `Most Expensive Price`
FROM ( SELECT *
       FROM tblqthdr C 
       INNER JOIN tblvendor V USING (VdCode)
       INNER JOIN tblqtdtl B USING (DocNo)
       INNER JOIN tblitem A USING (ItCode)
       WHERE V.ActInd='Y' ) subquery

https://dbfiddle.uk/?rdbms=mysql_8.0&fiddle=53cade7afe509dcde6f259e5c5ae3fa3

【讨论】：