Question

我有一个MySql SELECT查询，它使用了大约6个表，在所有2个表中有超过4000个记录，我使用的查询是：

SELECT DISTINCT r.*,
                p.name AS product,
                p.price,
                p.tax,
                l.name AS license_status,
                CONCAT(c.firstname, ' ', c.lastname) AS customer,
                CONCAT(cc.firstname, ' ', cc.lastname) AS license_customer,
                cc.telephone AS license_customer_mobile
FROM order_license r
LEFT JOIN customer c ON (c.customer_id = r.customer_id)
LEFT JOIN order_product p ON (p.order_id = r.order_id
                              AND r.product_id = p.product_id)
LEFT JOIN license_status l ON (l.license_status_id = r.license_status_id)
LEFT JOIN customer cc ON (cc.customer_id = r.license_customer_id)
WHERE r.license_status_id = '7'
  AND r.validity > 0
ORDER BY r.end_date ASC LIMIT 0,10

问题是它需要大约1分钟才能显示记录，这对于如此少的记录来说非常高。 MySql服务器是一个相当快的Linode VPS。现在我不知道什么是错的。

我尝试添加索引并删除LEFT JOINS（如下面的查询中所示），但结果几乎相同。

SELECT r.*,
       p.name AS product,
       p.price,
       p.tax,
       l.name AS license_status,
       CONCAT(c.firstname, ' ', c.lastname) AS customer,
       CONCAT(cc.firstname, ' ', cc.lastname) AS license_customer,
       cc.telephone AS license_customer_mobile
FROM order_license r,
     order_product p,
     license_status l,
     customer c,
     customer cc
WHERE (p.order_id = r.order_id
       AND r.product_id = p.product_id)
  AND (l.license_status_id = r.license_status_id)
  AND (c.customer_id = r.customer_id)
  AND (cc.customer_id = r.license_customer_id)
  AND r.license_status_id = '7'
  AND r.validity > 0
ORDER BY r.end_date ASC LIMIT 0,10

请帮忙。

Answer 1

您正在覆盖ON条款中的WHERE条件。

改变：

WHERE (p.order_id = r.order_id
   AND r.product_id = p.product_id)
AND (l.license_status_id = r.license_status_id)
AND (cc.customer_id = r.license_customer_id)
AND r.license_status_id = '7'
AND r.validity > 0
ORDER BY r.end_date ASC LIMIT 0,10

到

WHERE  r.license_status_id = '7' 
AND r.validity > 0 
ORDER BY r.end_date ASC LIMIT 0,10

Answer 2

你可以试试这段代码吗？如果没有帮助，请尽快回复

SELECT
  R.*,
  P.name  AS product,
  P.price,
  P.tax,
  L.name  AS license_status,
  CONCAT( C.firstname, ' ', C.lastname) AS customer
  CONCAT( CC.firstname, ' ', CC.lastname) AS license_customer
  CC.telephone AS license_customer_mobile
FROM order_license R
  LEFT JOIN customer C
    ON C.customer_id = R.customer_id
  LEFT JOIN order_product P
    ON P.order_id = R.order_id
      AND P.product_id = R.product_id
  LEFT JOIN license_status L
    ON L.license_status_id = R.license_status_id
  LEFT JOIN customer CC
    ON CC.customer_id = R.customer_id
WHERE R.validity > 0
    AND R.license_status_id = 7 
GROUP BY R.order_license_id
ORDER BY R.end_date LIMIT 10

如何改进多表SELECT查询？

2 个答案: