MariaDB中更新数据语句是什么 更新多列数据怎样实现
很多朋友都对“MariaDB中更新数据语句是什么,更新多列数据如何实现”的内容比较感兴趣,对此小编整理了相关的知识分享给大家做个参考,希望大家阅读完这篇文章后可以有所收获,那么感兴趣的朋友就继续往下看吧! 在MariaDB中,UPDATE语句用于通过更改表中的值来修改现有字段。 语法: UPDATE table_name SET field=new_value, field2=new_value2,... [WHERE ...] 或者,UPDATE语句可以与WHERE,ORDER BY和LIMIT子句一起使用。 UPDATE table SET column1 = expression1, column2 = expression2, ... [WHERE conditions] [ORDER BY expression [ ASC | DESC ]] [LIMIT number_rows]; 1. 更新单个列 假设我们有一个表 - students,并具有以下数据记录: MariaDB [testdb]> select * from students; +------------+--------------+-----------------+----------------+ | student_id | student_name | student_address | admission_date | +------------+--------------+-----------------+----------------+ | 1 | Maxsu | Haikou | 2017-01-07 | | 3 | JMaster | Beijing | 2016-05-07 | | 4 | Mahesh | Guangzhou | 2016-06-07 | | 5 | Kobe | Shanghai | 2016-02-07 | | 6 | Blaba | Shengzheng | 2016-08-07 | +------------+--------------+-----------------+----------------+ 5 rows in set (0.00 sec) 现在,更改student_id列的值为 6的行记录,把student_address列的值更新为:Shenzhen。 UPDATE Students SET student_address = 'Shenzhen' WHERE student_id = '6'; 执行上面更新语句后,查询更新的结果 - MariaDB [testdb]> UPDATE Students -> SET student_address = 'Shenzhen' -> WHERE student_id = '6'; Query OK, 1 row affected (0.21 sec) Rows matched: 1 Changed: 1 Warnings: 0
MariaDB [testdb]> select * from students where student_id=6; +------------+--------------+-----------------+----------------+ | student_id | student_name | student_address | admission_date | +------------+--------------+-----------------+----------------+ | 6 | Blaba | Shenzhen | 2016-08-07 | +------------+--------------+-----------------+----------------+ 1 row in set (0.08 sec) 2. 更新多列 还可以使用MariaDB数据库中的UPDATE语句来更新多个列。 在以下示例中,将更新表students中student_name为Kobe的两列 - student_name和student_address的值。参考以下更新语句 - UPDATE Students SET student_name = '科比', student_address = 'Haikou' WHERE student_name = 'Kobe'; 执行上面语句,得到以下结果 - MariaDB [testdb]> UPDATE Students -> SET student_name = '科比', student_address = 'Haikou' -> WHERE student_name = 'Kobe'; Query OK, 1 row affected (0.09 sec) Rows matched: 1 Changed: 1 Warnings: 0 -- 查询更新的结果 MariaDB [testdb]> select * from students; +------------+--------------+-----------------+----------------+ | student_id | student_name | student_address | admission_date | +------------+--------------+-----------------+----------------+ | 1 | Maxsu | Haikou | 2017-01-07 | | 3 | JMaster | Beijing | 2016-05-07 | | 4 | Mahesh | Guangzhou | 2016-06-07 | | 5 | 科比 | Haikou | 2016-02-07 | | 6 | Blaba | Shenzhen | 2016-08-07 | +------------+--------------+-----------------+----------------+ 5 rows in set (0.02 sec) 注意事项 在执行语句时,经常要指定更新的条件,如果忘记了指定了WHERE子句中的条件,那么将会更新所有行记录。想象一下,以下两个语句执行的效果 - -- 语句1 UPDATE Students SET student_name = '科比', student_address = 'Haikou' WHERE student_name = 'Kobe'; -- 语句2 UPDATE Students SET student_name = '科比', student_address = 'Haikou';除数据 到此这篇关于“MariaDB中更新数据语句是什么,更新多列数据如何实现”的文章就介绍到这了,更多相关MariaDB中更新数据语句是什么,更新多列数据如何实现内容,小编将为大家输出更多高质量的实用文章! (编辑:银川站长网) 【声明】本站内容均来自网络,其相关言论仅代表作者个人观点,不代表本站立场。若无意侵犯到您的权利,请及时与联系站长删除相关内容! |