如何在 SQL 中有条件地计算值

Question

我有一个实体属性值的索引表，如下所示： +-----------+--------------+----------+-------+ | entity_id | attribute_id | store_id | value | +-----------+--------------+----------+-------+ | 38 | 190 | 1 | 22 | | 38 | 190 | 1 | 23 | | 39 | 190 | 1 | 22 | | 39 | 190 | 1 | 23 | | 39 | 190 | 1 | 42 | | 40 | 190 | 1 | 22 | | 41 | 190 | 1 | 54 | | 42 | 190 | 1 | 54 | | 43 | 190 | 1 | 22 | | 44 | 190 | 1 | 22 | | 45 | 190 | 1 | 54 | +-----------+--------------+----------+-------+

如您所见，单个实体可以为单个属性具有多个值（entity_id38 具有 values 22,23）并且这些值对于每个实体不是唯一的（entity_id38,39 两者共享value 22)。

要解决的第一个问题是获取每个值的不同实体的数量；这很容易实现：

SELECT value, COUNT(entity_id) AS count
FROM catalog_product_index_eav
WHERE attribute_id=190
GROUP BY value;

导致： +-------+-------+ | value | count | +-------+-------+ | 22 | 5 | | 23 | 2 | | 42 | 1 | | 54 | 3 | +-------+-------+

我的问题是如何在此计数中嵌套 OR 条件，即：对于某些 特定 值 Y，对于每个值 X，计算具有值 X 或 Y 的实体的数量。

我想在单个查询中执行此操作。例如，对于attribute_id 190 和value 23，上述示例的输出应为： +-------+-------+ | value | count | +-------+-------+ | 22 | 5 | # all entities with value 22 happen to have 23 as well | 23 | 2 | that is, one is a subset of the other | 42 | 2 | # intersection is nonempty | 54 | 5 | # sets are disjoint +-------+-------+

Answer 1

select c1.value, 
( SELECT COUNT(DISTINCT entity_id) as count 
  FROM catalog_product_index_eav 
  where attribute_id=81 
  and (value=c1.value || value=7) ) as count 
FROM catalog_product_index_eav c1 
WHERE attribute_id=81 
GROUP BY c1.value

Answer 2

尝试使用

Select C.value, max(C.count) from (
SELECT A.value, (Select COUNT(B.entity_id) from FROM catalog_product_index_eav B
WHERE B.attribute_id=A.attribute_id and (B.value=A.value or B.value=23)) AS count
FROM catalog_product_index_eav A
WHERE A.attribute_id=190) C group by C.value

Answer 3

如果满足您的输出，它会在单个查询中为您提供两个结果。

SELECT i.value AS [value], COUNT(i.entity_id) AS [count], 
(SELECT COUNT(b.entity_id) tot FROM catalog_product_index_eav b
        WHERE b.entity_id IN (SELECT v.entity_id FROM 
        catalog_product_index_eav v WHERE v.VALUE = i.value)) AS [total_count]
FROM catalog_product_index_eav i
WHERE i.attribute_id=190
GROUP BY i.value