数据库之表操作

Posted 2021-01-11 13507215809qwer-

创建表

#语法：
create table 表名(
字段名1 类型[(宽度) 约束条件],
字段名2 类型[(宽度) 约束条件],
字段名3 类型[(宽度) 约束条件]
);

#注意：
1. 在同一张表中，字段名是不能相同
2. 宽度和约束条件可选
3. 字段名和类型是必须的

mysql> create database staff;
Query OK, 1 row affected (0.00 sec)

mysql> use staff;
Database changed
mysql> create table staff_info (id int,name varchar(50),age int(3),sex enum(‘male‘,‘female‘),phone bigint(11),job varchar(11));
Query OK, 0 rows affected (0.02 sec)


mysql> show tables;
+-----------------+
| Tables_in_staff |
+-----------------+
| staff_info      |
+-----------------+
1 row in set (0.00 sec)

mysql> desc staff_info;
+-------+-----------------------+------+-----+---------+-------+
| Field | Type                  | Null | Key | Default | Extra |
+-------+-----------------------+------+-----+---------+-------+
| id    | int(11)               | YES  |     | NULL    |       |
| name  | varchar(50)           | YES  |     | NULL    |       |
| age   | int(3)                | YES  |     | NULL    |       |
| sex   | enum(‘male‘,‘female‘) | YES  |     | NULL    |       |
| phone | bigint(11)            | YES  |     | NULL    |       |
| job   | varchar(11)           | YES  |     | NULL    |       |
+-------+-----------------------+------+-----+---------+-------+
6 rows in set (0.00 sec)

mysql> select id,name,sex from staff_info;
Empty set (0.00 sec)

mysql> select * from staff_info;
Empty set (0.00 sec)

插入数据

mysql> insert into staff_info (id,name,age,sex,phone,job) values (1,‘Alex‘,83,‘female‘,13651054608,‘IT‘);
Query OK, 1 row affected (0.00 sec)

mysql> insert into staff_info values (2,‘Egon‘,26,‘male‘,13304320533,‘Teacher‘);
Query OK, 1 row affected (0.00 sec)

mysql> insert into staff_info values (3,‘nezha‘,25,‘male‘,13332353222,‘IT‘),(4,‘boss_jin‘,40,‘male‘,13332353333,‘IT‘);
Query OK, 2 rows affected (0.00 sec)
Records: 2  Duplicates: 0  Warnings: 0

mysql> select * from staff_info;
+------+----------+------+--------+-------------+---------+
| id   | name     | age  | sex    | phone       | job     |
+------+----------+------+--------+-------------+---------+
|    1 | Alex     |   83 | female | 13651054608 | IT      |
|    2 | Egon     |   26 | male   | 13304320533 | Teacher |
|    3 | nezha    |   25 | male   | 13332353222 | IT      |
|    4 | boss_jin |   40 | male   | 13332353333 | IT      |
+------+----------+------+--------+-------------+---------+
4 rows in set (0.00 sec)

 

c代表此行作废

查案表结构

查看表结构有两种方式：

describe [tablename];这种方法和desc [tablename];效果相同；可以查看当前的表结构

虽然desc命令可以查看表的定义，但是其输出的信息还不够全面，为了得到更全面的表定义信息，有时候就需要查看创建表的SQL语句，使用show create table语法。除了可以看到表定义之外，还可以看到engine（存储引擎）和charset（字符集）等信息。（G选项的含义是是的记录能够竖向排列，以便更好的显示内容较长的记录。）

mysql> describe staff_info;
+-------+-----------------------+------+-----+---------+-------+
| Field | Type                  | Null | Key | Default | Extra |
+-------+-----------------------+------+-----+---------+-------+
| id    | int(11)               | YES  |     | NULL    |       |
| name  | varchar(50)           | YES  |     | NULL    |       |
| age   | int(3)                | YES  |     | NULL    |       |
| sex   | enum(‘male‘,‘female‘) | YES  |     | NULL    |       |
| phone | bigint(11)            | YES  |     | NULL    |       |
| job   | varchar(11)           | YES  |     | NULL    |       |
+-------+-----------------------+------+-----+---------+-------+
6 rows in set (0.00 sec)

mysql> desc staff_info;
+-------+-----------------------+------+-----+---------+-------+
| Field | Type                  | Null | Key | Default | Extra |
+-------+-----------------------+------+-----+---------+-------+
| id    | int(11)               | YES  |     | NULL    |       |
| name  | varchar(50)           | YES  |     | NULL    |       |
| age   | int(3)                | YES  |     | NULL    |       |
| sex   | enum(‘male‘,‘female‘) | YES  |     | NULL    |       |
| phone | bigint(11)            | YES  |     | NULL    |       |
| job   | varchar(11)           | YES  |     | NULL    |       |
+-------+-----------------------+------+-----+---------+-------+
6 rows in set (0.00 sec)

mysql> show create table staff_infoG;
*************************** 1. row ***************************
       Table: staff_info
Create Table: CREATE TABLE `staff_info` (
  `id` int(11) DEFAULT NULL,
  `name` varchar(50) DEFAULT NULL,
  `age` int(3) DEFAULT NULL,
  `sex` enum(‘male‘,‘female‘) DEFAULT NULL,
  `phone` bigint(11) DEFAULT NULL,
  `job` varchar(11) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8
1 row in set (0.01 sec)

ERROR: 
No query specified