mysql数据库基本命令---多条数据的同时操作

添加主键mysql> alter table info add primary key(id);Query OK, 0 rows affected (0.07 sec)Records: 0  Duplicates: 0  Warnings: 0mysql> desc info;  #查看主键+--------+--------------+------+-----+---------+-------+| Field  | Type         | Null | Key | Default | Extra |+--------+--------------+------+-----+---------+-------+| id     | int(11)      | NO   | PRI | NULL    |       |    #显示出主键| name   | char(6)      | YES  |     | NULL    |       || score  | decimal(5,2) | YES  |     | NULL    |       || age    | int(4)       | YES  |     | NULL    |       || hobbly | int(4)       | YES  |     | NULL    |       |+--------+--------------+------+-----+---------+-------+5 rows in set (0.00 sec)添加外键alter table info add constraint FK_ID foreign key(hobbly) REFERENCES hy(id);mysql> show index from info\G;    #查看外键* 2. row *        Table: info   Non_unique: 1     Key_name: FK_ID     #外键添加成功 Seq_in_index: 1  Column_name: hobbly    Collation: A  Cardinality: 3     Sub_part: NULL       Packed: NULL         Null: YES   Index_type: BTREE      Comment: Index_comment: 2 rows in set (0.00 sec)表格同时修改个字段（不同表列内容）update info set age=23,num=44 where id=2;   mysql> select * from info;+----+--------+-------+-----------+------+------+| id | name   | score | hobbly    | age  | num  |+----+--------+-------+-----------+------+------+|  1 | zl     | 88    | 看书      |   33 | NULL ||  2 | 李四   | 68    | 上网      |   23 |   44 |        #成功修改|  3 | 王四   | 68    | 看电视    | NULL | NULL |+----+--------+-------+-----------+------+------+3 rows in set (0.00 sec)同时增加多个字段mysql> alter table info add column age int,add column num int;Query OK, 0 rows affected (0.05 sec)Records: 0  Duplicates: 0  Warnings: 0mysql> desc info; #查看表结构+--------+----------+------+-----+---------+-------+| Field  | Type     | Null | Key | Default | Extra |+--------+----------+------+-----+---------+-------+| id     | int(11)  | NO   | PRI | NULL    |       || name   | char(4)  | YES  |     | NULL    |       || score  | char(6)  | YES  |     | NULL    |       || hobbly | char(10) | YES  |     | NULL    |       || age    | int(11)  | YES  |     | NULL    |       || num    | int(11)  | YES  |     | NULL    |       |+--------+----------+------+-----+---------+-------+同时删除多个字段mysql> alter table info drop column age,drop column num;Query OK, 0 rows affected (0.05 sec)Records: 0  Duplicates: 0  Warnings: 0mysql> select * from info;+----+--------+-------+-----------+| id | name   | score | hobbly    |+----+--------+-------+-----------+|  1 | zl     | 88    | 看书      ||  2 | 李四   | 68    | 上网      ||  3 | 王四   | 68    | 看电视    |+----+--------+-------+-----------+同时删除多个记录条数（多行）mysql> delete from info where id in (3,4);Query OK, 2 rows affected (0.00 sec)mysql> select * from info;+----+--------+-------+--------+| id | name   | score | hobbly |+----+--------+-------+--------+|  1 | zl     | 88    | 看书   ||  2 | 李四   | 68    | 上网   ||  5 | kl     | 88    | 游泳   |+----+--------+-------+--------+同时查看多条指定记录（行）mysql> select * from info where id in (3,4);+----+--------+-------+-----------+| id | name   | score | hobbly    |+----+--------+-------+-----------+|  3 | 王四   | 68    | 看电视    ||  4 | ll         | 67    | 看书      |+----+--------+-------+-----------+