mysql> select * from mytable; +----------+------+------------+-----------+ | name | sex | birth | birthaddr | +----------+------+------------+-----------+ | abccs |f | 1977-07-07 | china | | mary |f | 1978-12-12 | usa | | tom |m | 1970-09-02 | usa | +----------+------+------------+-----------+
· 2、创建第二个表title(包括作者、文章标题、发表日期):
mysql> create table title(writer varchar(20) not null, -> title varchar(40) not null, -> senddate date);
向该表中填加记录,最后表的内容如下: mysql> select * from title; +--------+-------+------------+ | writer | title | senddate | +--------+-------+------------+ | abccs | a1 | 2000-01-23 | | mary | b1 | 1998-03-21 | | abccs | a2 | 2000-12-04 | | tom | c1 | 1992-05-16 | | tom | c2 | 1999-12-12 | +--------+-------+------------+ 5 rows in set (0.00sec)
· 3、多表查询
现在我们有了两个表: mytable 和 title。利用这两个表我们可以进行组合查询: 例如我们要查询作者abccs的姓名、性别、文章: mysql> SELECT name,sex,title FROM mytable,title -> WHERE name=writer AND name=´abccs´; +-------+------+-------+ | name | sex | title | +-------+------+-------+ | abccs | f | a1 | | abccs | f | a2 | +-------+------+-------+
再举一个例子,用于查询文章a2的作者、出生地和出生日期: mysql> select title,writer,birthaddr,birth from mytable,title -> where mytable.name=title.writer and title=´a2´; +-------+--------+-----------+------------+ | title | writer | birthaddr | birth | +-------+--------+-----------+------------+ | a2 | abccs | china | 1977-07-07 | +-------+--------+-----------+------------+
· 修改和备份、批处理
有时我们要对数据库表和数据库进行修改和删除,可以用如下方法实现:
· 1、增加一列:
如在前面例子中的mytable表中增加一列表示是否单身single: mysql> alter table mytable add column single char(1);
· 2、修改记录
将abccs的single记录修改为“y”: mysql> update mytable set single=´y´ where name=´abccs´;
现在来看看发生了什么: mysql> select * from mytable; +----------+------+------------+-----------+--------+ | name | sex | birth | birthaddr | single | +----------+------+------------+-----------+--------+ | abccs |f | 1977-07-07 | china | y | | mary |f | 1978-12-12 | usa | NULL | | tom |m | 1970-09-02 | usa | NULL | +----------+------+------------+-----------+--------+
· 3、增加记录
前面已经讲过如何增加一条记录,为便于查看,重复与此: mysql> insert into mytable -> values (´abc´,´f´,´1966-08-17´,´china´,´n´); Query OK, 1 row affected (0.05 sec) 查看一下: mysql> select * from mytable; +----------+------+------------+-----------+--------+ | name | sex | birth | birthaddr | single | +----------+------+------------+-----------+--------+ | abccs |f | 1977-07-07 | china | y | | mary |f | 1978-12-12 | usa | NULL | | tom |m | 1970-09-02 | usa | NULL | | abc |f | 1966-08-17 | china | n | +----------+------+------------+-----------+--------+
· 3、删除记录
用如下命令删除表中的一条记录: mysql> delete from mytable where name=´abc´; DELETE从表中删除满足由where给出的条件的一条记录。
再显示一下结果: mysql> select * from mytable; +----------+------+------------+-----------+--------+ | name | sex | birth | birthaddr | single | +----------+------+------------+-----------+--------+ | abccs |f | 1977-07-07 | china | y | | mary |f | 1978-12-12 | usa | NULL | | tom |m | 1970-09-02 | usa | NULL | +----------+------+------------+-----------+--------+
· 4、删除表:
mysql> drop table ****(表1的名字),***表2的名字; 可以删除一个或多个表,小心使用。