MySQL之SQL语法及SQL解析顺序源码分析（sql的解释）

# 语法顺序

SELECT DISTINCT 内容来自samhan

<select_list> 本文来自zvvq

FROM

zvvq.cn

<left_table> <join_type> zvvq

JOIN <right_table> ON <join_condition> copyright zvvq

WHERE zvvq

<where_condition> zvvq.cn

GROUP BY

内容来自samhan666

<group_by_list> zvvq好，好zvvq

HAVING

<having_condition> 本文来自zvvq

ORDER BY

zvvq.cn

<order_by_condition>

本文来自zvvq

LIMIT <limit_number>

# 解析顺序 内容来自zvvq，别采集哟

FROM <left_table>

内容来自samhan

ON <join_condition> 内容来自zvvq，别采集哟

<join_type> JOIN <right_table>  -- 这一步和上一步，会循环执行 内容来自zvvq，别采集哟

WHERE <where_condition> -- 这一步会循环执行，多个条件从左往右

GROUP BY <group_by_list>

HAVING <having_condition>

内容来自samhan

SELECT   -- 分组之后才执行SELECT

内容来自zvvq，别采集哟

DISTINCT <select_list>

ORDER BY <order_by_condition> copyright zvvq

LIMIT <limit_number> -- 这一步是MySQL独有的语法，前面都是SQL92标准 zvvq

select * from seller join product;

select * from seller s join product p on s.id = p.id;

本文来自zvvq

select * from seller s right join product p on s.id = p.id; 本文来自zvvq

-- mysql 8 默认开启了 only_full_group_by

select version(),@@sql_mode; 内容来自samhan666

-- 需要把这个选项关掉，

set global sql_mode=&#39;STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_ENGINE_SUBSTITUTION&#39;;

set session sql_mode=&#39;STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_ENGINE_SUBSTITUTION&#39;;

-- 后执行group by 正常 内容来自samhan

select * from user group by name;

-- 下面无效 内容来自zvvq

select id, distinct name from user; 内容来自samhan666

-- 下面有效

select distinct name from user; 内容来自zvvq，别采集哟