Question

SELECT product_key.contact_email, product_key.client_name, product_key.status, product_key.key, payment.paymentdate, product_key.id, MAX(paymentdate) AS latest_payment, DATE_ADD(MAX(paymentdate), INTERVAL 1 MONTH) AS expiration_date 
FROM product_key LEFT OUTER JOIN payment ON payment.keyid=product_key.id 
WHERE product_key.status = 'purchased' AND expiration_date = DATE_ADD(NOW(), INTERVAL 10 DAY) GROUP BY product_key.id 
ORDER BY client_name asc

这是我的查询。我知道我不能在WHERE子句中使用别名，因为在SELECT之前首先读取了WHERE。但即使我使用这样的东西：

SELECT product_key.client_name, DATE_ADD(MAX(paymentdate), INTERVAL 1 MONTH) AS expiration_date 
FROM product_key LEFT OUTER JOIN payment ON payment.keyid=product_key.id 
WHERE DATE_ADD(MAX(paymentdate), INTERVAL 1 MONTH) = DATE_ADD(NOW(), INTERVAL 10 DAY) AND product_key.status = 'purchased' 
GROUP BY product_key.id 
ORDER BY client_name asc

还是一个错误。请帮忙。感谢。

Answer 1

由于您使用的是汇总MAX()，因此您应该使用HAVING子句而不是WHERE。假设除了你的查询是正确和有效的，你可以像这样重写它

SELECT product_key.client_name, 
       DATE_ADD(MAX(paymentdate), INTERVAL 1 MONTH) AS expiration_date 
  FROM product_key LEFT OUTER JOIN payment 
    ON payment.keyid=product_key.id 
   AND product_key.status = 'purchased' 
 GROUP BY product_key.id 
HAVING DATE_ADD(MAX(paymentdate), INTERVAL 1 MONTH) = DATE_ADD(NOW(), INTERVAL 10 DAY) 
 ORDER BY client_name

或

SELECT product_key.client_name, 
       DATE_ADD(MAX(paymentdate), INTERVAL 1 MONTH) AS expiration_date 
  FROM product_key LEFT OUTER JOIN payment 
    ON payment.keyid=product_key.id 
   AND product_key.status = 'purchased' 
 GROUP BY product_key.id 
HAVING expiration_date = DATE_ADD(NOW(), INTERVAL 10 DAY) 
 ORDER BY client_name

Answer 2

您不能使用select子句中where子句中定义的别名。但这没关系，因为你想使用having子句：

SELECT pk.contact_email, pk.client_name, pk.status, pk.key, p.paymentdate, pk.id,
       MAX(paymentdate) AS latest_payment,
       DATE_ADD(MAX(paymentdate), INTERVAL 1 MONTH) AS expiration_date 
FROM product_key pk LEFT OUTER JOIN
     payment p
     ON p.keyid = pk.id 
WHERE pk.status = 'purchased'
GROUP BY pk.id 
HAVING expiration_date = DATE_ADD(NOW(), INTERVAL 10 DAY)
ORDER BY client_name asc;

你可以使用having子句中的别名。此外，我在您的查询中添加了表别名，以使其更具可读性。

WHERE子句中的查询错误

2 个答案: