6.1
SELECT
product_name,
purchase_price
FROM
Product
WHERE
purchase_price NOT IN (500, 2800, 5000);
返回4条结果
SELECT
product_name,
purchase_price
FROM
Product
WHERE
purchase_price NOT IN (500, 2800, 5000, NULL);
不返回任何结果
6.2
SELECT
sum(
CASE
WHEN sale_price <= 1000 THEN
1
ELSE
0
END
) AS low_price,
sum(
CASE
WHEN sale_price BETWEEN 1001
AND 3000 THEN
1
ELSE
0
END
) AS mid_price,
sum(
CASE
WHEN sale_price >= 3001 THEN
1
ELSE
0
END
) AS high_price
FROM
product;
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