基於案例理解MySQL執行計劃

MySQL SQL · 發表 2018-11-27 17:09:54

摘要：版權宣告：本文為博主原創文章，歡迎擴散，擴散請務必註明出處。 https://blog.csdn.net/robinson_0612/article/details/84569447 一、執行計劃一些參考連結 mysql explain type連線型別示例...

版權宣告：本文為博主原創文章，歡迎擴散，擴散請務必註明出處。 https://blog.csdn.net/robinson_0612/article/details/84569447

一、執行計劃一些參考連結

ofollow,noindex" target="_blank">mysql explain type連線型別示例

SQL/">MySQL EXPLAIN SQL 輸出資訊描述

二、獲取SQL執行計劃

方法1（命令列）：EXPLAIN sql_statement

方法2（Toad）：Toad裡邊在SQL編輯器裡邊點選explain plan

方法3（Navicate）Navicate裡邊點選解釋

三、案例

1、原始SQL及完整執行計劃

原始SQL語句：
SELECT c.customerNumber, c.customerName, e.lastname
FROM customers c
INNER JOIN employees e ON c.salesRepEmployeeNumber = e.employeeNumber
WHERE e.lastname LIKE 'T%'
AND EXISTS
(SELECT orderNumber, SUM(priceEach * quantityOrdered)
FROM orderdetails INNER JOIN orders USING (orderNumber)
WHERE customerNumber = c.customerNumber
GROUP BY orderNumber
HAVING SUM(priceEach * quantityOrdered) > 50000)
UIO/">NION
SELECT customerNumber, customerName, 'NULL'
FROM customers
WHERE customerName LIKE 'T%'

執行計劃截圖