Question

我有一个包含重复行的表。我想在删除之前更新行，只是为了确保删除好的行。

删除查询是这样的，有效：

DELETE FROM cscart_products 
WHERE updated_timestamp 
NOT IN (SELECT * 
    FROM (SELECT MAX(n.updated_timestamp) 
    FROM cscart_products n 
    GROUP BY n.product_code) x)

示例表：

product_code    product_type    status    updated_timestamp
DUSP1893        P               A         1551
DUSP1893        P               A         322
AH324444        P               A         555
AH324444        P               A         21332

某些产品具有相同的product_code。我想更新那些具有较小的updated_timestamp的状态从状态A到H.

谢谢你

Answer 1

您必须在交易中执行此操作。 1.开始交易 2.更新 3.删除 4.提交交易

START TRANSACTION;
UPDATE cscart_products SET status="H" WHERE updated_timestamp<some_value AND product_code IN (code1,code2,....codeN);
DELETE FROM cscart_products WHERE status="H" AND product_code IN (code1,code2,....codeN);
COMMIT;

Answer 2

首先获取时间戳较小的行，然后更新这些记录，如下所示：

UPDATE cscart_products
INNER JOIN (
  SELECT product_code pc, MIX(updated_timestamp) ts
  FROM cscart_products
  GROUP BY product_code
) t
ON cscart_products.product_code = t.pc 
AND cscart_products.updated_timestamp = t.ts
SET status = 'H'

内部查询将为您提供具有较小时间戳的product_code行。

Answer 3

它不应该比这更复杂：

-- mark the rows for which the updated_timestamp is smaller
-- than the maximum timestamp for that product_code
UPDATE cscart_products 
SET status = 'H'
WHERE updated_timestamp 
NOT IN (SELECT * 
    FROM (SELECT MAX(n.updated_timestamp) 
    FROM cscart_products n 
    GROUP BY n.product_code) x);

-- delete the marked rows (or don't, whatever you feel like)
DELETE FROM cscart_products 
WHERE status = 'H';

Answer 4

更新product_code中重复的最小updated_timestamp，状态为“H”

UPDATE cscart_products SET status='H'
WHERE updated_timestamp IN
(SELECT * FROM(SELECT MIN(updated_timestamp) FROM cscart_products  
GROUP BY product_code HAVING COUNT(product_code)>1)  X);

MySQL Update如果重复行

4 个答案: