数据类型基本介绍
- 数值类型
整形类型：tinyint,int,bigint
浮点类型：float,double
- 字符串类型
char系列：char varchar
text系列：text
blob系列：blob
枚举类型：ENUM
集合类型：SET
- 时间日期型
date time datetime timestamp year
- tinyint和int整形测试
mysql> create table test1(tinyint_test tinyint,int_test int);
Query OK, 0 rows affected (0.03 sec)
mysql> desc test1;
+--------------+------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+--------------+------------+------+-----+---------+-------+
| tinyint_test | tinyint(4) | YES | | NULL | |
| int_test | int(11) | YES | | NULL | |
+--------------+------------+------+-----+---------+-------+
2 rows in set (0.05 sec)
mysql> insert into test1 values(111,111);
Query OK, 1 row affected (0.01 sec)
mysql> select * from test1;
+--------------+----------+
| tinyint_test | int_test |
+--------------+----------+
| 111 | 111 |
+--------------+----------+
1 row in set (0.00 sec)
mysql> insert into test1(tinyint_test) values(128);
ERROR 1264 (22003): Out of range value for column 'tinyint_test' at row 1
mysql> insert into test1(int_test) values(mysql> insert into test1(int_test) values(2147483647);
Query OK, 1 row affected (0.01 sec)
mysql> insert into test1(int_test) values(2147483648);
ERROR 1264 (22003): Out of range value for column 'int_test' at row 1
- 整形宽度测试
mysql> create table test2(id1 int,id2 int(8));
mysql> desc test2;
+-------+---------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+---------+------+-----+---------+-------+
| id1 | int(11) | YES | | NULL | |
| id2 | int(8) | YES | | NULL | |
+-------+---------+------+-----+---------+-------+
mysql> insert into test2 values(1,1);
mysql> select * from test2;
+------+------+
| id1 | id2 |
+------+------+
| 1 | 1 |
+------+------+
mysql> create table test3(id1 int zerofill,id2 int(8) zerofill);
mysql> insert into test3 values(123456789,123456789);
mysql> select * from test3;
+------------+-----------+
| id1 | id2 |
+------------+-----------+
| 0123456789 | 123456789 |
+------------+-----------+
总结：整形宽度总是做填充使用，没有实际意义
- 浮点数类型测试-float
mysql> create table test1(float_test float(5,2)); //一共5位，也就是整数+小数一共5位，同时小数最多2位
mysql> insert into test1 values(1000.123);
ERROR 1264 (22003): Out of range value for column 'float_test' at row 1
mysql> insert into test1 values(999.123);
mysql> select * from test1;
+------------+
| float_test |
+------------+
| 999.12 |
+------------+
- 时间类型测试
date:年月日
time：时分秒
datetime：年月日时分秒
timestamp：如果传入的值是null，打印的是当前时间
mysql> create table test1(d date,t time,dt datetime);
mysql> desc test1;
+-------+----------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+----------+------+-----+---------+-------+
| d | date | YES | | NULL | |
| t | time | YES | | NULL | |
| dt | datetime | YES | | NULL | |
+-------+----------+------+-----+---------+-------+
mysql> insert into test1 values(now(),now(),now());
mysql> select * from test1;
+------------+----------+---------------------+
| d | t | dt |
+------------+----------+---------------------+
| 2018-04-17 | 14:50:54 | 2018-04-17 14:50:54 |
+------------+----------+---------------------+
mysql> create table test1(timestamp_test timestamp);
mysql> insert into test1 values(null);
mysql> select * from test1;
+---------------------+
| timestamp_test |
+---------------------+
| 2018-04-17 15:15:52 |
+---------------------+
- 字符串类型：char varchar ，注意字符串类型插入值需要使用引号
char：固定长度，插入的字符不足指定的范围，使用空格填充
varchar：列中的值可变长度
mysql> create table test1(c char(4),v varchar(4));
mysql> insert into test1 values('abcde','abcde');
ERROR 1406 (22001): Data too long for column 'c' at row 1
mysql> insert into test1 values('abcd','abcd');
- 枚举类型和集合类型 enum和set
ENUM：单选
SET：多选
mysql> create table test1(name varchar(50),sex enum('m','f'),hobby set('book','music','disc','game'));
mysql> desc test1;
+-------+-----------------------------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+-----------------------------------+------+-----+---------+-------+
| name | varchar(50) | YES | | NULL | |
| sex | enum('m','f') | YES | | NULL | |
| hobby | set('book','music','disc','game') | YES | | NULL | |
+-------+-----------------------------------+------+-----+---------+-------+
mysql> insert into test1 values('wf','m','music,book');
mysql> insert into test1 values('jack','m','film');
ERROR 1265 (01000): Data truncated for column 'hobby' at row 1
- 查看创表语句
mysql> show create table test1G
*************************** 1. row ***************************
Table: test1
Create Table: CREATE TABLE `test1` (
`name` varchar(50) DEFAULT NULL,
`sex` enum('m','f') DEFAULT NULL,
`hobby` set('book','music','disc','game') DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1
1 row in set (0.00 sec)
- 总结
int(10) ：没有实际意义
char(10),varchar(10),float(5,2) 有意义