MySQL学习笔记
文章目录
1 GBase 8s数据类型
2 GBase 8s内置数据类型
3 数据类型演示
—3.1 创建员工信息表
database mydb;
create table t_employee(
f_employeeid serial,
f_employeename varchar(50),
f_age int,
f_weight float,
f_height decimal(18,6),
f_salary money,
f_joindate date,
f_inputdate datetime year to second);
—3.2 验证serial数据类型
插入三条记录，只输入员工姓名
insert into t_employee(f_employeename) values('Tom');
insert into t_employee(f_employeename) values('Jack');
insert into t_employee(f_employeename) values('Mary');
查询员工ID和员工姓名
> select f_employeeid, f_employeename from t_employee;
f_employeeid f_employeename
1 Tom
2 Jack
3 Mary
3 row(s) retrieved.
>
结论：在不提供Serial字段数值情况下，Serial字段会自动为新插入记录生成一个递增数值。
插入两条记录，输入员工ID和员工姓名
insert into t_employee(f_employeeid, f_employeename) values(5, 'Henry'); insert into t_employee(f_employeeid, f_employeename) values(8, 'Rose');
查询员工ID和员工姓名
> select f_employeeid, f_employeename from t_employee;
f_employeeid f_employeename
1 Tom
2 Jack
3 Mary
5 Henry
8 Rose
5 row(s) retrieved.
>
结论：在提供Serial字段数值情况下，新插入记录的Serial字段使用提供的数值，不再自动生成新值。
插入一条记录，只输入员工姓名
insert into t_employee(f_employeename) values('Bill');
查询员工ID和员工姓名
> select f_employeeid, f_employeename from t_employee;
f_employeeid f_employeename
1 Tom
2 Jack
3 Mary
5 Henry
8 Rose
9 Bill
6 row(s) retrieved.
>
结论：当新插入的数据未提供Serial字段数值时，新记录的Serial字段值为当前表记录最大值加1。
插入一条记录，输入员工ID和员工姓名
insert into t_employee(f_employeeid, f_employeename) values(6, 'Kate');
查询员工ID和员工姓名
> select f_employeeid, f_employeename from t_employee;
f_employeeid f_employeename
1 Tom
2 Jack
3 Mary
5 Henry
8 Rose
9 Bill
6 Kate
7 row(s) retrieved.
>
插入一条记录，输入员工姓名
insert into t_employee(f_employeename) values('Bob');
查询员工ID和员工姓名
> select f_employeeid, f_employeename from t_employee;
f_employeeid f_employeename
1 Tom
2 Jack
3 Mary
5 Henry
8 Rose
9 Bill
6 Kate
10 Bob
8 row(s) retrieved.
>
结论：当Serial字段数值出现【空位置】时，可以指定确定的值进入插入。
—3.3 验证money类型
更新Bill的f_salary字段
update t_employee set f_salary = 1234567890.1234 where f_employeeid = 9;
查询员工ID,员工姓名，薪水
> select f_employeeid, f_employeename, f_salary from t_employee where f_employeeid > 8; f_employeeid 9 f_employeename Bill f_salary RMB 1234567890.12 f_employeeid 10 f_employeename Bob f_salary 2 row(s) retrieved. >
unload to '/home/gbasedbt/employee.txt' delimiter ',' select f_employeeid, f_employeename, f_salary from t_employee where f_employeeid > 8;
结论：Money类型会根据本地化设置，自动显示相应的货币符号和保留对应的小数位数，但数据本身仍然是一个定点小数，并不存储有关货币符号的信息。
—3.4 验证date类型
默认的date类型格式为月/日/年（如06/18/2020），当未设置任何有关date数据类型的环境变量时
> update t_employee set f_joindate = '06/18/2020' where f_employeeid = 1; 1 row(s) updated.
执行date数据操作时，如果日期格式不匹配，可能出现下面的错误
> update t_employee set f_joindate = '2020-06-18' where f_employeeid = 1; 1205: Invalid month in date Error in line 1 Near character position 69 >
设置如下环境变量，设置自己使用的日期格式
export GL_DATE="%iY-%m-%d"
再次执行更新操作
> !echo $GL_DATE
%iY-%m-%d
> update t_employee set f_joindate = '2020-06-18' where f_employeeid = 1;
1 row(s) updated.
> select f_employeeid, f_employeename,f_joindate from t_employee where f_employeeid = 1;
f_employeeid f_employeename f_joindate
1 Tom 2020-06-18
1 row(s) retrieved.
>
结论：GBase 8s可以根据数据中日期的具体格式，设置对应的GL_DATE，完成日期格式的输入。
—3.5 验证datetime类型
默认的datetime类型格式为【2020-06-18 12:34:56】
update t_employee set f_inputdate = '2020-06-18 12:34:56' where f_employeeid = 2;
直接使用年月日时分秒的格式（如2020-06-18 12:34:56），更新datetime字段。
> update t_employee set f_inputdate = '2020-06-18 12:34:56' where f_employeeid = 2; 1 row(s) updated. > select f_employeeid, f_employeename,f_inputdate from t_employee where f_employeeid = 2; f_employeeid 2 f_employeename Jack f_inputdate 2020-06-18 12:34:56 1 row(s) retrieved. >
—3.6 验证int,float,decimal类型
通过员工ID，更新员工年龄
update t_employee set f_age = 28 where f_employeeid = 1;
查询员工ID,员工姓名，年龄
> update t_employee set f_age = 28 where f_employeeid = 1;
1 row(s) updated.
> select f_employeeid, f_employeename, f_age from t_employee where f_employeeid = 1;
f_employeeid f_employeename f_age
1 Tom 28
1 row(s) retrieved.
>
通过员工ID，更新员工体重
update t_employee set f_weight = 56.78 where f_employeeid = 1;
查询员工ID,员工姓名，体重
> update t_employee set f_weight = 56.78 where f_employeeid = 1; 1 row(s) updated. > select f_employeeid, f_employeename, f_weight from t_employee where f_employeeid = 1; f_employeeid 1 f_employeename Tom f_weight 56.78000000000 1 row(s) retrieved. >
通过员工ID，更新员工身高
update t_employee set f_height = 1.86 where f_employeeid = 1;
查询员工ID,员工姓名，身高
> update t_employee set f_height = 1.86 where f_employeeid = 1; 1 row(s) updated. > select f_employeeid, f_employeename, f_height from t_employee where f_employeeid = 1; f_employeeid 1 f_employeename Tom f_height 1.860000 1 row(s) retrieved. >
4 总结
GBase 8s 支持多种数据类型。
GBase 8s 的基本数据类型，多数与其它数据库产品兼容。
GBase 8s 提供了一些特有的数据类型，如Serial，Money，方便用户使用。
GBase 8s 的日期时间类型，可通过环境变量设置，定义日期时间格式，方便用户使用。