mysql 执行顺序

Question

请问一下上面语句的执行顺序是什么>

sum是最后一步执行的么？

LEFT JOIN 之后

ON

WHERE

AND

这三个条件是先判断那个一的?

Answer 1

on后的先判断，where后的写在前面的先判断编号是执行顺序 (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>