mysql执行顺序

Mysql语法顺序，即当sql中存在下面的关键字时，它们要保持这样的顺序：

1. select[distinct]
2. from
3. join（如left join）
4. on
5. where
6. group by
7. having
8. union
9. order by
10. limit

Mysql执行顺序，即在执行时sql按照下面的顺序进行执行：

1. from
2. on
3. join
4. where
5. group by
6. having
7. select
8. distinct
9. union
10. order by