MariaDB FROM
子句用于从表中获取数据。它也被用来连接表,这将在后面章节中学习。
语法:
SELECT columns_names FROM table_name;
示例1:
假设要从"students"
表中检索所有学生信息。参考以下语句中,From
语句的用法 –
SELECT * FROM students;
执行上面查询语句,得到以下结果 –
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 | Kobe | Shanghai | 2016-02-07 |
| 6 | Blaba | Shengzhen | 2016-08-07 |
| 7 | Maxsu | Sanya | 2017-08-08 |
| 8 | Maxsu | Haikou | 2015-11-17 |
+------------+--------------+-----------------+----------------+
7 rows in set (0.00 sec)
示例2:
从students表中选择一个特定的列。例如,要选择student_id
和student_name
列,如下查询语句 –
SELECT student_id,student_name FROM students;
执行上面查询语句,得到以下结果 –
MariaDB [testdb]> SELECT student_id,student_name FROM students;
+------------+--------------+
| student_id | student_name |
+------------+--------------+
| 1 | Maxsu |
| 3 | JMaster |
| 4 | Mahesh |
| 5 | Kobe |
| 6 | Blaba |
| 7 | Maxsu |
| 8 | Maxsu |
+------------+--------------+
7 rows in set (0.00 sec)