MySql（十二）Sql92和Sql99的区别

青旅半醒 2022-10-02 12:55 378阅读 0赞

# sql92和sql99比较 #

1.功能方面：sql99支持的较多  
2.可读性：sql99实现了连接条件和筛选条件的分离，因此可读性较高

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQzOTUyMjQ1_size_16_color_FFFFFF_t_70][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQzOTUyMjQ1_size_16_color_FFFFFF_t_70 1][]

进阶练习：

![rc7wgp.png][]

/**查询编号大于3的女神的男朋友信息，如果有则列出详细信息，如果没有则用null补充**/
    SELECT bea.id,bea.name,b.*
    FROM beauty bea
    LEFT OUTER JOIN boys b
    ON bea.'boyfriend_id' = b.'id'
    WHERE bea.id > 3;
    /**查询哪个城市没有部门**/
    SELECT city
    FROM location l
    LEFT OUTER JOIN department d
    ON l.'location_id' = d.'location_id'
    WHERE d.'department_id' IS NULL;
    /**查询部门名为SAL或IT的员工信息**/
    SELECT e.* ,d.department_name
    FROM departments d
    LEFT OUTER JOIN employees e
    ON d.'department_id'= e.'department_id'
    WHERE d.department_name IN ('SAL','IT');

![5w9y5d.jpg][]

本文原文地址：[https://blog.csdn.net/qq\_43952245/article/details/90485688][https_blog.csdn.net_qq_43952245_article_details_90485688]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQzOTUyMjQ1_size_16_color_FFFFFF_t_70]: /images/20220112/86353023e8694735a18e46dfc1fbd0da.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQzOTUyMjQ1_size_16_color_FFFFFF_t_70 1]: /images/20220112/e73917a114ec4802b5017d5501e1aaf0.png
[rc7wgp.png]: /images/20220112/5619025459bd4dd9b5d0f88b6e3fbad4.png
[5w9y5d.jpg]: /images/20220112/5688791c306d4f76ad39c860f5965428.png
[https_blog.csdn.net_qq_43952245_article_details_90485688]: https://blog.csdn.net/qq_43952245/article/details/90485688