Question

目前使用SQLite3遇到问题

SELECT item_id, SUM(qoh), MIN(price), MAX(price), item_size
FROM inventory
WHERE item_size IS NULL OR item_size = 'S';

上述查询无效，只会返回NULL个值，而不会返回S。

SELECT item_id, SUM(qoh), MIN(price), MAX(price), item_size
FROM inventory
WHERE item_size = 'S'

以上显然会返回S

SELECT item_id, SUM(qoh), MIN(price), MAX(price), item_size
FROM inventory
WHERE item_size = 'S'OR item_size IS NULL;

以上只返回{{1}}值

我试图完成下面的等价物，

NULL

但在一个命令中，由于SELECT item_id, SUM(qoh), MIN(price), MAX(price), item_size FROM inventory WHERE item_size IS NULL; SELECT item_id, SUM(qoh), MIN(price), MAX(price), item_size FROM inventory WHERE item_size = 'S';的性质，只返回WHERE column IS NULL OR column = 'value'或＆＃39;值＆＃39;由于null影响算法的性质，

对我来说，SQL法律是否允许我绕过NULL从根本上不起作用？

Answer 1

使用

SELECT item_id, SUM(qoh), MIN(price), MAX(price), item_size
FROM inventory
WHERE coalesce(item_size, 'S') = 'S'
GROUP BY  coalesce(item_size, 'S') -- will add nulls to S or
-- GROUP BY  coalesce(item_size, 'null') - will add them as 'null' but filter them out by your where

您的问题是使用sum隐式group by - 并且null与字符串不能很好地组合 - 您必须明确group by合并后的值才能将空值分组到S

SQL WHERE是NULL或column =＆＃39; value＆＃39;

1 个答案: