SQL搜寻语句执行顺序的示例分析

      这篇文章主要介绍SQL查询语句执行顺序的示例分析，文中介绍的非常详细，具有一定的参考价值，感兴趣的小伙伴们一定要看完！
 
SQL查询语句执行顺序如下：
 
(7) SELECT
(8) DISTINCT <select_list>
(1) FROM <left_table>
(3) <join_type> JOIN <right_table>
(2) ON <join_condition>
(4) WHERE <where_condition>
(5) GROUP BY <group_by_list>
(6) HAVING <having_condition>
(9) ORDER BY <order_by_condition>
(10) LIMIT <limit_number>
前期准备工作
 
 新建一个测试数据库
 
create database testData;
 
准备SQL逻辑查询测试语句
 
SELECT a.user_id,COUNT(b.order_id) as total_orders
FROM user as a
LEFT JOIN orders as b
ON a.user_id = b.user_id
WHERE a.city = 'beijing'
GROUP BY a.user_id
HAVING COUNT(b.order_id) < 2
ORDER BY total_orders desc
使用上述SQL查询语句来获得来自北京，并且订单数少于2的客户;
 
在这些SQL语句的执行过程中，都会产生一个虚拟表，用来保存SQL语句的执行结果。