Question

我有一个有效的查询，但似乎可以/应该以更优雅的方式重写。问题是，由于HAVING声明，我还没有办法做到这一点。

我只想看一下顾客购买的3家商店中的哪一家，并为他们指定一家主店。＆＃39;

我结束了UNION 7个不同的案件......它有点荒谬。

在我完美的世界中，我能够以某种方式使用HAVING . . OR HAVING . .，但这似乎与MySQL的哲学不符。

SELECT Cust_ID, 'Main_store_1' AS Main_Store, sum(StoreName = 'Store_1') as num_Store_1, sum(StoreName = 'Store_2') as num_Store_2, sum(StoreName = 'Store_3') as num_Store_3
FROM shopping_table 
WHERE Cust_ID in (<some list of Cust_IDs>)
AND StoreName in ('Store_1', 'Store_2', 'Store_3')
GROUP BY Cust_ID 
HAVING num_Store_1 > 1 and num_Store_2 = 0 and Store_3 = 0
UNION 
SELECT Cust_ID, 'Main_store_2' AS Main_Store, sum(StoreName = 'Store_1') as num_Store_1, sum(StoreName = 'Store_2') as num_Store_2, sum(StoreName = 'Store_3') as num_Store_3
FROM shopping_table 
WHERE Cust_ID in (<some list of Cust_IDs>)
AND StoreName in ('Store_1', 'Store_2', 'Store_3')
GROUP BY Cust_ID 
HAVING num_Store_1 = 0 and num_Store_2 > 0 and Store_3 = 0

和建议/哲学意见将不胜感激。感谢。

Answer 1

没有完全重写（我很确定有更好的方法，但它可能相当冗长），这种修改应该有效：

SELECT q.*
, CASE 
  WHEN (num_Store_1 > 1 and num_Store_2 = 0 and Store_3 = 0)
  THEN 'Main_store_1'
  WHEN (num_Store_1 = 0 and num_Store_2 > 0 and Store_3 = 0)
  THEN 'Main_store_2'
  WHEN [more conditions]
  THEN [another string]
  ELSE 'No Main'
  END AS Main_Store
FROM (
  SELECT Cust_ID
    , sum(StoreName = 'Store_1') as num_Store_1
    , sum(StoreName = 'Store_2') as num_Store_2
    , sum(StoreName = 'Store_3') as num_Store_3
  FROM shopping_table 
  WHERE Cust_ID in (<some list of Cust_IDs>)
    AND StoreName in ('Store_1', 'Store_2', 'Store_3')
  GROUP BY Cust_ID 
) AS q
;

Answer 2

试试这个：

...HAVING (num_Store_1 > 1 and num_Store_2 = 0 and Store_3 = 0) OR (num_Store_1 = 0 and num_Store_2 > 0 and Store_3 = 0)

Answer 3

你真的只有兴趣列出在一家商店独家购物的顾客，然后可以使用：

SELECT      Cust_ID, 
            Max(StoreName) as Main_Store, 
            Sum(StoreName = 'Store_1') as num_Store_1,
            Sum(StoreName = 'Store_2') as num_Store_2,
            Sum(StoreName = 'Store_3') as num_Store_3
FROM        shopping_table 
WHERE       Cust_ID in (<some list of Cust_IDs>)
AND         StoreName in ('Store_1', 'Store_2', 'Store_3')
GROUP BY    Cust_ID
HAVING      Count(DISTINCT StoreName) = 1

或者，如果您还要列出其他客户，并选择他们访问过的最重要商店作为他们的主要商店，那么请使用CASE每个商店WHEN，降序优先顺序：

SELECT      Cust_ID, 
            CASE
                WHEN Sum(StoreName = 'Store_1') > 0 THEN 'Store_1'
                WHEN Sum(StoreName = 'Store_2') > 0 THEN 'Store_2'
                WHEN Sum(StoreName = 'Store_3') > 0 THEN 'Store_3'
            END as Main_Store,
            Sum(StoreName = 'Store_1') as num_Store_1,
            Sum(StoreName = 'Store_2') as num_Store_2,
            Sum(StoreName = 'Store_3') as num_Store_3
FROM        shopping_table 
WHERE       Cust_ID in (<some list of Cust_IDs>)
AND         StoreName in ('Store_1', 'Store_2', 'Store_3')
GROUP BY    Cust_ID

在MySQL查询中进行HAVING的多个条件

3 个答案: