MariaDB中WHERE的用法是怎样 怎样与条件一起应用
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关于“MariaDB中WHERE的用法是怎样，如何与条件一起应用”的知识有一些人不是很理解，对此小编给大家总结了相关内容，具有一定的参考借鉴价值，而且易于学习与理解，希望能对大家有所帮助，有这个方面学习需要的朋友就继续往下看吧。 在MariaDB中，WHERE子句与SELECT，INSERT，UPDATE和DELETE语句一起使用来选择或更改想要更改的满足指定特定行记录。 它是一个在表名后面出现的语句。 语法 [COMMAND] field,field2,... FROM table_name,table_name2,... WHERE [CONDITION] 注意：WHERE子句是一个可选的子句。它可以和AND，OR，AND & OR，LIKE运算符一起使用。 1. WHERE子句与单一条件 示例： 我们有一个表students，里边有一些数据。假设要查询students表中的student_id小于6的所有记录。 SELECT * FROM Students WHERE student_id < 6; 执行上面查询语句，得到以下结果 - MariaDB [testdb]> SELECT * -> FROM Students -> WHERE student_id < 6; +------------+--------------+-----------------+----------------+ | 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 | +------------+--------------+-----------------+----------------+ 4 rows in set (0.00 sec) 2. WHERE子句与AND条件 为了方便演示，这里再插入一条数据 - INSERT INTO students (student_name, student_address, admission_date) VALUES('Maxsu','Sanya','2017-08-08 00:00:00'); 当前students表中的全部数据是 - 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 | Shengzhen | 2016-08-07 | | 7 | Maxsu | Sanya | 2017-08-08 | +------------+--------------+-----------------+----------------+ 6 rows in set (0.00 sec) 现在要查询students表中的所有列，其中student_name是Maxsu，并且student_id大于1的行记录。这两个条件都必须满足。参考以下查询语句 - SELECT * FROM Students WHERE student_name = 'Maxsu' AND student_id >1 ; 执行上面查询语句，得到以下结果 - MariaDB [testdb]> SELECT * -> FROM Students -> WHERE student_name = 'Maxsu' -> AND student_id >1 ; +------------+--------------+-----------------+----------------+ | student_id | student_name | student_address | admission_date | +------------+--------------+-----------------+----------------+ | 7 | Maxsu | Sanya | 2017-08-08 | +------------+--------------+-----------------+----------------+ 1 row in set (0.03 sec) 3. WHERE子句与OR条件 现在要查询students表中的所有列，其中student_name是Maxsu，或者student_id大于5的行记录。这两个条件满足其中一个即可。参考以下查询语句 - SELECT * FROM Students WHERE student_name = 'Maxsu' OR student_id >5 ; 执行上面查询语句，得到以下结果 - MariaDB [testdb]> SELECT * -> FROM Students -> WHERE student_name = 'Maxsu' -> OR student_id >5 ; +------------+--------------+-----------------+----------------+ | student_id | student_name | student_address | admission_date | +------------+--------------+-----------------+----------------+ | 1 | Maxsu | Haikou | 2017-01-07 | | 6 | Blaba | Shengzhen | 2016-08-07 | | 7 | Maxsu | Sanya | 2017-08-08 | +------------+--------------+-----------------+----------------+ 3 rows in set (0.00 sec) 4. WHERE子句与OR/AND条件 假设要查询students表中的所有列，那些符合student_name是Ajeet，student_id大于或等于1，或者student_address是Shanghai的行记录。 SELECT * FROM Students WHERE student_name = 'Maxsu' AND student_id >=1 OR (student_address = 'Shanghai'); 执行上面查询语句，得到以下结果 - MariaDB [testdb]> SELECT * -> FROM Students -> WHERE student_name = 'Maxsu' -> AND student_id >=1 -> OR (student_address = 'Shanghai'); +------------+--------------+-----------------+----------------+ | student_id | student_name | student_address | admission_date | +------------+--------------+-----------------+----------------+ | 1 | Maxsu | Haikou | 2017-01-07 | | 5 | Kobe | Shanghai | 2016-02-07 | | 7 | Maxsu | Sanya | 2017-08-08 | +------------+--------------+-----------------+----------------+ 3 rows in set (0.00 sec) 以上就是关于“MariaDB中WHERE的用法是怎样，如何与条件一起应用”的介绍了，感谢各位的阅读。 （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! |
