MySQL第一次实验的一些操作

还是别人不要看系列2333333

 

 

mysql> SHOEDATABASES

   -> ;

ERROR 1064 (42000): You have an error inyour SQL syntax; check the manual that corresponds to your MySQL server versionfor the right syntax to use near 'SHOE DATABASES' at line 1

mysql> SHOW DATABASES;

+--------------------+

| Database           |

+--------------------+

| information_schema |

| mysql              |

| performance_schema |

| t1                 |

| test               |

+--------------------+

5 rows in set (0.00 sec)

 

mysql> USE test;

Database changed

mysql> SELECT DATABASE();

+------------+

| DATABASE() |

+------------+

| test      |

+------------+

1 row in set (0.00 sec)

 

mysql> CREATETABLE IF NOT EXISTS tb1(

    -> username VARCHAR(20),

    -> age TINYINT UNSIGNED,

    -> salary FLOAT(8,2) UNSIGNED

    -> );

Query OK, 0 rows affected (0.18 sec)

 

mysql> SHOWTABLES

   -> ;

+----------------+

| Tables_in_test |

+----------------+

| tb1            |

+----------------+

1 row in set (0.00 sec)

 

mysql> SHOW TABLES;

+----------------+

| Tables_in_test |

+----------------+

| tb1            |

+----------------+

1 row in set (0.00 sec)

 

mysql> SHOWTABLES FROM mysql;

+---------------------------+

| Tables_in_mysql           |

+---------------------------+

| columns_priv              |

| db                        |

| event                     |

| func                      |

| general_log               |

| help_category             |

| help_keyword              |

| help_relation             |

| help_topic                |

| host                      |

| ndb_binlog_index          |

| plugin                    |

| proc                      |

| procs_priv                |

| proxies_priv              |

| servers                   |

| slow_log                  |

| tables_priv               |

| time_zone                 |

| time_zone_leap_second     |

| time_zone_name            |

| time_zone_transition      |

| time_zone_transition_type |

| user                      |

+---------------------------+

24 rows in set (0.00 sec)

 

mysql> SELECTDATABASE();

+------------+

| DATABASE() |

+------------+

| test      |

+------------+

1 row in set (0.00 sec)

 

mysql> showcolumns from tb1;(对表的操作都没有进入到特定的表内而是要制定一个表)

+----------+---------------------+------+-----+---------+-------+

| Field   | Type                | Null | Key| Default | Extra |

+----------+---------------------+------+-----+---------+-------+

| username | varchar(20)         | YES |     | NULL    |      |

| age     | tinyint(3) unsigned | YES |     | NULL    |      |

| salary  | float(8,2) unsigned | YES |     | NULL    |      |

+----------+---------------------+------+-----+---------+-------+

3 rows in set (0.09 sec)

 

mysql> DESC tb1;

+----------+---------------------+------+-----+---------+-------+

| Field   | Type                | Null | Key| Default | Extra |

+----------+---------------------+------+-----+---------+-------+

| username | varchar(20)         | YES |     | NULL    |      |

| age     | tinyint(3) unsigned | YES |     | NULL    |      |

| salary  | float(8,2) unsigned | YES |     | NULL    |      |

+----------+---------------------+------+-----+---------+-------+

3 rows in set (0.05 sec)

 

mysql> SELECT DATABASE();

+------------+

| DATABASE() |

+------------+

| test      |

+------------+

1 row in set (0.00 sec)

 

mysql> INSERTtb1 VALUES('Tom',23,1000.2);

Query OK, 1 row affected (0.11 sec)

 

mysql> SHOW COLUMNS FROM tb1;

+----------+---------------------+------+-----+---------+-------+

| Field   | Type                | Null | Key| Default | Extra |

+----------+---------------------+------+-----+---------+-------+

| username | varchar(20)         | YES |     | NULL    |      |

| age     | tinyint(3) unsigned | YES |     | NULL    |      |

| salary  | float(8,2) unsigned | YES |     | NULL    |      |

+----------+---------------------+------+-----+---------+-------+

3 rows in set (0.02 sec)

 

mysql> INSERTtb1(username,salary)VALUES('JHON',233);

Query OK, 1 row affected (0.06 sec)

 

mysql> SELECT *FROM tb1;（关于ＳＥＬＥＣＴ　语句以后会有＝更详尽的介绍）

+----------+------+---------+

| username | age  | salary |

+----------+------+---------+

| Tom     |   23 | 1000.20 |

| JHON    | NULL |  233.00 |

+----------+------+---------+

2 rows in set (0.00 sec)

 

1 row in set (0.00 sec)

 

mysql> CREATETABLE tb2(（指定的数据成员是否必须要插入）

    -> username VARCHAR(20) NOT NULL,

    -> age TINYINT UNSIGNED NULL

    -> );

Query OK, 0 rows affected (0.10 sec)

 

mysql> SHOW TABLES;

+----------------+

| Tables_in_test |

+----------------+

| tb1            |

| tb2            |

+----------------+

2 rows in set (0.00 sec)

 

mysql> INSERT tb1(age) VALUES(20.0);

Query OK, 1 row affected (0.06 sec)

 

mysql> INSERT tb2(age) VALUES(20);

ERROR 1364 (HY000): Field 'username'doesn't have a default value

mysql> DESC tb2;

+----------+---------------------+------+-----+---------+-------+

| Field   | Type                | Null | Key| Default | Extra |

+----------+---------------------+------+-----+---------+-------+

| username | varchar(20)         | NO  |     | NULL    |      |

| age     | tinyint(3) unsigned | YES |     | NULL    |      |

+----------+---------------------+------+-----+---------+-------+

2 rows in set (0.03 sec)

 

mysql> select * tb2;

ERROR 1064 (42000): You have an error inyour SQL syntax; check the manual that corresponds to your MySQL server versionfor the right syntax to use near 'tb2' at line 1

mysql> select * from tb2;

Empty set (0.00 sec)

 

mysql>