MySQL查詢重新設計

Question

我有以下查詢選擇notes表中輸入（例如：bob）不在orders表中的所有內容。

SELECT * FROM `notes` WHERE notes.customer_email NOT IN 
(SELECT customers_email_address FROM orders) 
AND ((customer_phone LIKE '%bob%') 
OR (customer_name LIKE '%bob%') 
OR (customer_email LIKE '%bob%')) 
AND customers_id IS NULL 
GROUP BY `customer_email` 
ORDER BY `customer_name` 
DESC LIMIT 50 

查詢的這個胖男孩在我的開發機器上花費約80秒，在服務器上花約7秒鐘。

兩個問題：

1. 我做了什麼錯此查詢？ （我需要從我的錯誤中學習）
2. 我該如何改進此查詢？

Answer 1

嘗試使用加入：

SELECT * 
FROM 
    `notes` left join orders 
    on notes.customer_email=orders.customers_email_address 
WHERE 
    orders.customers_email_address is null 
    AND notes.customers_id IS NULL 
    AND ((customer_phone LIKE '%bob%') 
     OR (customer_name LIKE '%bob%') 
     OR (customer_email LIKE '%bob%')) 
ORDER BY `customer_name` 
DESC LIMIT 50 

他們通常比IN/NOT IN子句快。而且，我也不確定你爲什麼在這裏放置一個小組。