虽然我们在写sql查询语句的时候是按照select开始的，但是对于MySQL数据库机读的顺序并不是我们所写的或者所想那样也是从select开始的。

1、手写顺序

SELECT DISTINCT
    <select_list>
FROM
    <left_table> <join_type>
JOIN <right_table> ON <join_cndition>
WHERE
     <where_condition>
GROUP BY 
     <group_by_list>
HAVING 
     <having_condition>
ORDER BY 
     <order_by_condition>
LIMIT <limit_number>

2、机读顺序

FROM <left_table>
ON <join_condition>
<join_type> JOIN <right_table>
WHERE <where_condition>
GROUP BY  <group_by_list>
HAVING <having_condition>
SELECT 
DISTINCT <select_list>
ORDER BY <order_by_condition>
LIMIT <limit_number>