Question

我正在使用postgresql。

我有一个名为custom_field_answers的表。数据看起来像这样

Id | product_id | value      | number_value | 
4  | 2          |            | 117          |
3  | 1          |            | 107          |
2  | 1          | bangle     |              |
1  | 2          | necklace   |              |

我想找到所有产品，其text_value为'bangle'，number_value小于50.

这是我的第一次尝试。

SELECT "products".* FROM "products" INNER JOIN "custom_field_answers" 
ON "custom_field_answers"."product_id" = "products"."id" 
WHERE ("custom_field_answers"."value" ILIKE 'bangle')

这是我的第二次尝试。

 SELECT "products".* FROM "products" INNER JOIN "custom_field_answers" 
ON "custom_field_answers"."product_id" = "products"."id" 
where ("custom_field_answers"."number_value" < 50)

这是我最后的尝试。

SELECT "products".* FROM "products" INNER JOIN "custom_field_answers" 
ON "custom_field_answers"."product_id" = "products"."id" 
WHERE ("custom_field_answers"."value" ILIKE 'bangle') 
AND ("custom_field_answers"."number_value" < 50)

但这不会选择任何产品记录。

Answer 1

它不生成任何记录，因为没有符合这两个标准的custom_field_answers记录。你想要的是一张在表格中有必要记录的product_id列表。为了防止没有人为你编写SQL，直到我有机会自己解决这个问题，我想我至少会向你解释为什么你的查询无效。

Answer 2

WHERE子句一次只能查看一行中的列。

因此，如果您需要一个适用于表中两个不同行的条件，则需要连接到该表两次，这样就可以从两个行中获取列。

SELECT p.*
FROM "products" AS p
INNER JOIN "custom_field_answers" AS a1 ON p."id" = a1."product_id"
INNER JOIN "custom_field_answers" AS a2 ON p."id" = a1."product_id" 
WHERE a1."value" = 'bangle' AND a2."number_value" < 50

Answer 3

这应该有效：

SELECT p。* FROM products LEFT JOIN custom_field_answers c ON（c.product_id = p.id AND c.value LIKE'％bangle％'AND c.number_value

希望有所帮助

Answer 4

与手镯相关的number_value字段为空，因此在这些情况下您将无法进行直接比较。相反，首先将空值转换为0。

SELECT "products".* FROM "products" INNER JOIN "custom_field_answers" 
ON "custom_field_answers"."product_id" = "products"."id" 
WHERE ("custom_field_answers"."value" LIKE '%bangle%') 
AND (coalesce("custom_field_answers"."number_value", 0) < 50)

Answer 5

实际上没有测试它，但这个一般的想法应该有效：

SELECT *
FROM products
WHERE
    EXISTS (
        SELECT *
        FROM custom_field_answers
        WHERE
            custom_field_answers.product_id = products.id
            AND value = 'bangle'
    )
    AND EXISTS (
        SELECT *
        FROM custom_field_answers
        WHERE
            custom_field_answers.product_id = products.id
            AND number_value < 5
    )

用简单的英语：获取所有产品......

custom_field_answers中有value = 'bangle'
custom_field_answers number_value < 5。

如何查找具有特定多属性值的所有产品

5 个答案: