mysql数据类型

Posted 2020-10-31 你很棒

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 |
  +------------+