MySQL中表的基本操作2

 mysql> insert into teacher
     -> values (202, 'robot', 'ZhuHai', '2013-04-24');
 Query OK, 1 row affected (0.00 sec)
 
 mysql> insert into teacher
     -> values (203, 'Jack', 'ZhuHai', '2013-04-24');
 Query OK, 1 row affected (0.00 sec)
 
 mysql> insert into teacher
     -> values (204, 'Ann', 'ZhuHai', '2013-04-24');
 Query OK, 1 row affected (0.01 sec)
 
 mysql> insert into teacher
     -> values (205, 'Rose', 'ZhuHai', '2013-04-24');
 Query OK, 1 row affected (0.01 sec)

（1）统计有多少条记录

 mysql> select count(*) from teacher;
 +----------+
 | count(*) |
 +----------+
 |        4 |
 +----------+
 row in set (0.01 sec)
 
 mysql> select * from teacher;
 +-----+-------+---------+------------+
 | Id  | name  | address | year       |
 +-----+-------+---------+------------+
 | 202 | robot | ZhuHai  | 2013-04-24 |
 | 203 | Jack  | ZhuHai  | 2013-04-24 |
 | 204 | Ann   | ZhuHai  | 2013-04-24 |
 | 205 | Rose  | ZhuHai  | 2013-04-24 |
 +-----+-------+---------+------------+
 rows in set (0.00 sec)

（2）投影操作，选择需要查看的信息

 mysql> select Id, year from teacher;
 +-----+------------+
 | Id  | year       |
 +-----+------------+
 | 202 | 2013-04-24 |
 | 203 | 2013-04-24 |
 | 204 | 2013-04-24 |
 | 205 | 2013-04-24 |
 +-----+------------+
 rows in set (0.00 sec)

 mysql> select Id, name from teacher;
 +-----+-------+
 | Id  | name  |
 +-----+-------+
 | 202 | robot |
 | 203 | Jack  |
 | 204 | Ann   |
 | 205 | Rose  |
 +-----+-------+
 rows in set (0.00 sec)

（3）预览功能，显示字段中一部分的信息

 mysql> select Id, left(address, 3) from teacher;
 +-----+------------------+
 | Id  | left(address, 3) |
 +-----+------------------+
 | 202 | Zhu              |
 | 203 | Zhu              |
 | 204 | Zhu              |
 | 205 | Zhu              |
 +-----+------------------+
 rows in set (0.00 sec)
 
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