用于创建视图的mysql查询

Question

这是我的代码：

create DATABASE assignment

CREATE TABLE Books (
    id INTEGER PRIMARY KEY,
    category TEXT,
    price FLOAT CHECK (price>0), 
    promoted bit DEFAULT 1
);

INSERT INTO Books (id, category, price) VALUES (1, 'Dictionary', 100); 
INSERT INTO Books (id, category, price) VALUES (2, 'Dictionary', 150); 
INSERT INTO Books (id, category, price) VALUES (3, 'Science', 120); 
INSERT INTO Books (id, category, price) VALUES (4, 'Science', 190); 
INSERT INTO Books  (id, category, price) VALUES (5, 'Science', 320);

CREATE VIEW PromotionSummary AS
SELECT category, MIN(price) AS minprice , MAX(price) AS maxprice 
FROM Books
WHERE promoted
GROUP BY category;

面对此错误：

Msg 4145，第15级，状态1，程序升级摘要，第5行在需要“ GROUP”附近的条件中指定的非布尔类型的表达式。

我现在正在使用azure数据库。

Answer 1

错误消息表明您正在使用SQL Server，而不是MySQL。如果是这样，则需要在promoted的谓词上输入一个值（MySQL会允许该值，但SQL Server不允许）。想必您想要：

CREATE VIEW PromotionSummary AS 
SELECT category, MIN(price) AS minprice , MAX(price) AS maxprice 
FROM Books 
WHERE promoted = 1 
GROUP BY category;