mysql_语法总结(二)
--------+-------------+------+-----+---------+-------+
4 rows in set
我们增加了birthday字段，并且类型为date类型。
现在我们需要删除birthday字段：
mysql> alter table student drop column birthday; Query OK, 0 rows affected Records: 0 Duplicates: 0 Warnings: 0
查看表结构：
mysql> desc student; +-------+-------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-------+-------------+------+-----+---------+-------+ | id | int(11) | NO | PRI | NULL | | | name | varchar(20) | NO | UNI | NULL | | | age | int(11) | YES | | NULL | | +-------+-------------+------+-----+---------+-------+ 3 rows in set
说明删除成功！
现在向student表中插入数据：
mysql> insert into student values(1,'hongten',20); Query OK, 1 row affected mysql> insert into student(id,name,age) values(2,'hanyuan',30); Query OK, 1 row affected
这两中方式，都是向student表中插入数据，第一种方式没有写出字段名称，而后面的值是所有字段的值。
而第二种方式是把字段都写了出来，后面跟的是字段对于的值。
现在查询student表：
mysql> select * from student; +----+---------+-----+ | id | name | age | +----+---------+-----+ | 1 | hongten | 20 | | 2 | hanyuan | 30 | +----+---------+-----+ 2 rows in set
可以看出我们刚才插入的两组数据已经保存到数据库中了，现在对一个字段查询：
mysql> select name from student; +---------+ | name | +---------+ | hanyuan | | hongten | +---------+ 2 rows in set
上面只是针对name字段的查询；
现在进行条件查询：
mysql> select name,age from student where id = 2; +---------+-----+ | name | age | +---------+-----+ | hanyuan | 30 | +---------+-----+ 1 row in set
针对student表中的name，age查询，条件是id=2的记录；
现在查询student表中的记录总数：
mysql> select count(*) from student; +----------+ | count(*) | +----------+ | 2 | +----------+ 1 row in set
查询不同name的student：
mysql> select distinct(name) from student; +---------+ | name | +---------+ | hanyuan | | hongten | +---------+ 2 rows in set
修改id=2的name字段：
mysql> update student set name = 'Tom' where id =2; Query OK, 1 row affected Rows matched: 1 Changed: 1 Warnings: 0
查询student表：
mysql> select * from student; +----+---------+-----+ | id | name | age | +----+---------+-----+ | 1 | hongten | 20 | | 2 | Tom | 30 | +----+---------+-----+ 2 rows in set
现在删除id=2 的记录：
mysql> delete from student where id = 2; Query OK, 1 row affected mysql> select * from student; +----+---------+-----+ | id | name | age | +----+---------+-----+ | 1 | hongten | 20 | +----+---------+-----+ 1 row in set