與循環

Question

MySQL的計數行我有如下表：

+-------------+--------------+ 
| product  | purchased | 
+-------------+--------------+ 
| Hammer  | <timestamp> | 
| Nipper  | <timestamp> | 
| Saw   | <timestamp> | 
| Nipper  | <timestamp> | 
| Hammer  | <timestamp> | 
| Hammer  | <timestamp> | 
| Saw   | <timestamp> | 
| Saw   | <timestamp> | 
| Saw   | <timestamp> | 
+-------------+--------------+ 

我希望看到一個關於這些產品的保修狀態摘要。保修期應從購買日起5年。因此，今天的日期應該有可能檢查產品是否在保修期內（基於購買日期）。此外，我想現在當最後買的產品將超出保修期。下面是一個示例表：

+-------------+--------------+----------------+------------------+------------------+ 
| product  | count  | warranty valid | warranty expired | last p. warranty | 
+-------------+--------------+----------------+------------------+------------------+ 
| Hammer  | 3   | 1    | 2    | 10.03.2015  | 
| Nipper  | 2   | 2    | -    | 01.01.2014  | 
| Saw   | 4   | 1    | 3    | 02.12.2013  | 
+-------------+--------------+----------------+------------------+------------------+ 

我試圖創建這個例子的查詢，但我不知道每個產品的結果如何循環計數有效warrantys等。這就是我目前的樣子：

SELECT 
    product, 
    date_format(from_unixtime(purchased), '%d.%m.%Y') AS purchaseDate, 
    date_format(date_add(from_unixtime(purchased), INTERVAL 5 YEAR), '%d.%m.%Y') AS warrantyEnd, 
    (
     SELECT 
      COUNT(product) 
     FROM 
      productWarranty 
    ) AS count 
FROM 
    productWarranty s 
GROUP BY 
    product 

我不知道怎麼寫的子查詢，因爲我需要用的東西等，其中產品=錘。但是，我怎麼能告訴sql來循環每一個產品？

Answer 1

這是我張貼在您other question

SELECT p2c.pid AS productNumber, 
     p.name AS productName, 
     COUNT(*) AS registered, 
     SUM(date_add(from_unixtime(purchased), INTERVAL 5 YEAR) >= CURDATE()) AS inWarranty, 
     SUM(date_add(from_unixtime(purchased), INTERVAL 5 YEAR) < CURDATE()) AS outOfWarranty, 
     DATE_FORMAT(MAX(from_unixtime(purchased)), '%d.%m.%Y') AS lastPurchased, 
     DATE_FORMAT(date_add(MAX(from_unixtime(purchased)), INTERVAL 5 YEAR), '%d.%m.%Y') AS warrantyUntil 
FROM products2customers p2c 
JOIN products p ON p.id = p2c.pid 
GROUP BY p2c.pid 
ORDER BY inWarranty DESC 

Answer 2

更好normalization將大大加快這一查詢，但這裏有一個例子從工作：

首先，你需要啓動你的基本查詢，一個將推動的結果。在這種情況下，它的所有產品在表中列出：

SELECT DISTINCT product 
FROM productWarranty 

上面的語句創建一種「臨時」表中，我們可以立足於我們的查詢。如果你有一個單獨的，規範化的產品表，那會更好。

列的其餘部分可以簡單地子查詢的基表驅動：

總計數：

SELECT COUNT(*) 
FROM productWarranty 
WHERE product = 'Hammer' 

總有效保證：

SELECT COUNT(*) 
FROM productWarranty 
WHERE product = 'Hammer' 
    AND purchased >= <warranty cut-off date> 

總到期擔保：

SELECT COUNT(*) 
FROM productWarranty 
WHERE product = 'Hammer' 
    AND purchased < <warranty cut-off date> 

最後一次購買日期：

SELECT MAX(purchased) 
FROM productWarranty 
WHERE product = 'Hammer' 

我們所有的這些組合成一個單一的查詢：

SELECT Base.product 
    , (
      SELECT COUNT(*) 
      FROM productWarranty 
      WHERE product = Base.product 
     ) AS TotalCount 
    , (
      SELECT COUNT(*) 
      FROM productWarranty 
      WHERE product = Base.product 
       AND date_add(from_unixtime(purchased), INTERVAL 5 YEAR) >= CURDATE() 
     ) AS ValidWarrantyCount 
    , ( 
      SELECT COUNT(*) 
      FROM productWarranty 
      WHERE product = Base.product 
       AND date_add(from_unixtime(purchased), INTERVAL 5 YEAR) < CURDATE() 
     ) AS ExpiredWarrantyCount 
    , (
      SELECT MAX(purchased) 
      FROM productWarranty 
      WHERE product = Base.product 
     ) AS LastPurchased 
FROM (
      SELECT DISTINCT product 
      FROM productWarranty 
     ) AS Base 

Answer 3

你需要使用的是什麼保修是否仍然有效或過期，保修日期，所以你首先需要建立一個反映了一個表：

select product 
     , IF(warranty >= NOW(), 1, 0) as valid 
     , IF(warranty < NOW(), 1, 0) as expired 
     , warranty as last 
from  (
      select product 
       , ADDDATE(purchased, INTERVAL 5 YEAR) as warranty 
      from  productWarranty 
     ) w 
group by product 
; 

這將讓你類似的東西：

+---------+-------+---------+---------------------+ 
| product | valid | expired | warranty   | 
+---------+-------+---------+---------------------+ 
| Hammer |  1 |  0 | 2017-01-01 00:00:00 | 
| Nipper |  1 |  0 | 2017-01-01 00:00:00 | 
| Nipper |  1 |  0 | 2017-01-01 00:00:00 | 
| Nipper |  1 |  0 | 2017-01-01 00:00:00 | 
| Saw  |  1 |  0 | 2017-01-01 00:00:00 | 
| Saw  |  0 |  1 | 2011-01-01 00:00:00 | 
| Saw  |  1 |  0 | 2017-01-01 00:00:00 | 
| Saw  |  1 |  0 | 2017-01-01 00:00:00 | 
+---------+-------+---------+---------------------+ 

然後使用聚合函數來篩選和總結你正在尋找的信息：

select product 
     , SUM(IF(warranty >= NOW(), 1, 0)) as valid 
     , SUM(IF(warranty < NOW(), 1, 0)) as expired 
     , MAX(warranty) as last 
from  (
      select product 
        , adddate(purchased, interval 5 year) as warranty 
      from productWarranty 
     ) w 
group by product 
; 

+---------+-------+---------+---------------------+ 
| product | valid | expired | last    | 
+---------+-------+---------+---------------------+ 
| Hammer |  1 |  0 | 2017-01-01 00:00:00 | 
| Nipper |  3 |  0 | 2017-01-01 00:00:00 | 
| Saw  |  3 |  1 | 2017-01-01 00:00:00 | 
+---------+-------+---------+---------------------+