每个人都写过无数的sql语句，那你是否清晰的了解，它是如果运行的呢？机器的运行和编写sql语句有什么关系呢？
1.sql的执行顺序
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| 手写的顺序：
SELECT DISTINCT
<select_list>
FROM
<left table> <join type>
JOIN <right_table> ON <join_codition>
WHERE
<where_condition>
HAVING
<having_condition>
ORDER BY
<order_by_condition>
LIMIT
<limit number>
|
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| 机读的顺序：
1 FROM <left_table>
2 ON <join_condition>
3 <join_type> JOIN <right_table>
4 WHERE <where_condition>
5 GROUP BY <group by_list>
6 HAVING <having_condition>
7 SELECT
8 DISTINCT <select_list>
9 ORDER BY <order_by_condition>
10 LIMIT <limit_number>
|
