mysql - 0行影响MySQL中的UPDATE语句

嗨，我有一条更新语句，我试图将meta_key数量的数量从3以上减少到3（meta_value），每执行一次，我就会收到“ 0行受影响”的信息。

UPDATE usermeta
INNER JOIN cov on cov.user_id = usermeta.user_id
SET usermeta.meta_value = '3'
WHERE usermeta.meta_key = 'quantity'
  AND usermeta.meta_value > '3'
  AND cov.end_date = '2017-05-18'
-- this is the query to see the rows I want changed
SELECT cov.*, usermeta.meta_value
FROM cov
 INNER JOIN usermeta
    ON     cove.user_id = usermeta.user_id
       AND meta_key = 'quantity'
WHERE cov.end_date = '2017-05-18' and usermeta.meta_value > 3
ORDER BY end_date

谁能看到我做错了吗？谢谢！

最佳答案

'3'和3之间有区别。因此，我将从以下内容开始：

UPDATE usermeta um INNER JOIN
       cov
       ON cov.user_id = um.user_id
    SET um.meta_value = '3'
WHERE um.meta_key = 'quantity' AND
      um.meta_value + 0 > 3 AND
      cov.end_date = '2017-05-18';