Managing Data in Different Time Zones 管理数据在不同的时区
you should be able to:
1、Use data types similar to DATE that store fractional seconds and track time zones
2、Use data types that store the difference between two datetime values
3、Use the following datetime functions:
CURRENT_DATE
CURRENT_TIMESTAMP
LOCALTIMESTAMP
DBTIMEZONE
SESSIONTIMEZONE
EXTRACT
TZ_OFFSET
FROM_TZ 转换为时区类型
TO_TIMESTAMP
TO_YMINTERVAL 间隔年到月
TO_DSINTERVAL 间隔天到秒
用户会话的时间：current_date, current_timestamp, localtimestamp
select sessiontimezone from dual;
ALTER SESSION SET TIME_ZONE = '-05:00';
ALTER SESSION SET TIME_ZONE = dbtimezone;
ALTER SESSION SET TIME_ZONE = local;
ALTER SESSION SET TIME_ZONE = 'America/New_York';
毫秒最大精度：9位，默认6位。
select hire_date from emp where rownum<5;
alter table emp modify hire_date timestamp(9);
ALTER SESSION SET NLS_DATE_FORMAT = 'DD-MON-YYYY HH24:MI:SS';
ALTER SESSION SET TIME_ZONE = '-5:00';
SELECT SESSIONTIMEZONE, CURRENT_DATE FROM DUAL;
SELECT SESSIONTIMEZONE, CURRENT_TIMESTAMP FROM DUAL;
SELECT SESSIONTIMEZONE, LOCALTIMESTAMP FROM DUAL;
SELECT DBTIMEZONE FROM DUAL;
SELECT SESSIONTIMEZONE FROM DUAL;
CREATE TABLE web_orders (order_date TIMESTAMP WITH TIME ZONE, delivery_time TIMESTAMP WITH LOCAL TIME ZONE);
INSERT INTO web_orders values (current_date, current_timestamp + 2);
SELECT * FROM web_orders;
INTERVAL Data Types 间隔时间类型
INTERVAL data types are used to store the difference between two datetime values.
There are two classes of intervals:
Year-month
Day-time
The precision of the interval is:
The actual subset of fields that constitutes an interval
Specified in the interval qualifier
例：
CREATE TABLE warranty
(prod_id number, warranty_time INTERVAL YEAR(3) TO MONTH);
INSERT INTO warranty VALUES (123, INTERVAL '8' MONTH);
INSERT INTO warranty VALUES (155, INTERVAL '200' YEAR(3));
INSERT INTO warranty VALUES (678, '200-11');
SELECT * FROM warranty;
例：
CREATE TABLE lab
( exp_id number, test_time INTERVAL DAY(2) TO SECOND);
INSERT INTO lab VALUES (100012, '90 00:00:00');
INSERT INTO lab VALUES (56098,
INTERVAL '6 03:30:16' DAY TO SECOND);
SELECT * FROM lab;
例：
SELECT last_name, employee_id, hire_date
FROM employees
WHERE EXTRACT(YEAR FROM TO_DATE(hire_date, 'DD-MON-RR')) > 2007
ORDER BY hire_date;
例：
SELECT last_name, hire_date,
EXTRACT (MONTH FROM HIRE_DATE)
FROM employees
WHERE manager_id = 100;
例：
SELECT TZ_OFFSET('US/Eastern'),
TZ_OFFSET('Canada/Yukon'),
TZ_OFFSET('Europe/London')
FROM DUAL;
例：
SELECT FROM_TZ(TIMESTAMP
'2000-07-12 08:00:00', 'Australia/North')
FROM DUAL;
例：
SELECT TO_TIMESTAMP ('2007-03-06 11:00:00', 'YYYY-MM-DD HH:MI:SS') FROM DUAL;
例：
SELECT hire_date,
hire_date + TO_YMINTERVAL('01-02') AS HIRE_DATE_YMININTERVAL FROM employees WHERE department_id = 20;
例：
SELECT last_name,
TO_CHAR(hire_date, 'mm-dd-yy:hh:mi:ss') hire_date,
TO_CHAR(hire_date +
TO_DSINTERVAL('100 10:00:00'),
'mm-dd-yy:hh:mi:ss') hiredate2
FROM employees;
DST 夏年时，中国未用了