Date data type and Globalization in Oracle

https://ir.linkedin.com/in/masoud-haji-hassan-pour
By:
Masoud Haji Hassan Pour
Date data type
and Globalization
in Oracle

Agenda
• Describe Date data type
• Formatting Date data type
• Arithmetic on Date data type
• Single row functions
• Oracle Globalization
• Date consideration in flashback

Describe Date data type
SQL> select sysdate from dual;
SYSDATE
---------
11-FEB-17
DD-MON-RR is default format for retrieving Date data type in oracle and based on
NLS_TERRITORY.

Content
Century
Year
Month
Day
Hour
Minute
Second

SQL> create table test (c1 date);
Table created.
SQL> insert into test values(sysdate);
1 row created.
SQL> commit;
Commit complete.
SQL> select * from test;
C1
---------
11-FEB-17
SQL> select to_char(c1, 'cc yyyy-mm-dd hh24:mi:ss') as mydate from test;
MYDATE
----------------------
21 2017-02-11 14:07:25

Inserting or updating a date value in a table will implicitly use truncated month
SQL> insert into test values (sysdate);
1 row created.
SQL> insert into test values (to_date('12','mi'));
1 row created.
SQL> select to_char(c1, 'cc yyyy-mm-dd hh24:mi:ss') as mydate from test;
MYDATE
----------------------
21 2017-02-11 15:55:38
21 2017-02-01 00:12:00

Minimum and Maximum Date value in Oracle:
January 1, 4712 BCE ~ December 31, 9999 CE

Formatting Date data type
Format Mask Format Description
DD Day of the month
MON Month of the year
YY Two-digit year
YYYY Four-digit year including century
RR Two-digit year (Year 2000-compliant)
CC Two-digit century
HH Hours with AM and PM
HH24 Twenty-four-hour time
MI Minute
SS Seconds

Example:
SQL> select * from test;
C1
---------
01-NOV-59
12-FEB-17
12-FEB-17
SQL> select to_char(c1, 'cc yyyy-mm-dd
hh24:mi:ss') as mydate from test;
MYDATE
----------------------
20 1959-11-01 00:00:00
21 2017-02-12 08:58:02
21 2017-02-12 08:58:11
SQL> select to_char(c1, 'cc q') as mydate
from test;
MYDA
----
20 4
21 1
21 1

Standard Syntaxes:
to_char(date, [format], [nls_parameter]),
to_date(string, [format], [nls_parameter]),

Date Format Masks for Days, Months, and Years:
Format Element Description Result
Year Case-sensitive spelling of year Twenty Seventeen
Mon Three-letter abbreviation of month Jun
Month Case-sensitive spelling of month June
Dy Three-letter abbreviation of day Mon
Day Case-sensitive spelling of day Monday

Miscellaneous Date Format Masks:
Format Element Description Result
- / . , ? # ! Punctuation marks: 'MM.YY' 09.08
"any character
literal"
Character literals:
'"Week" W "of " Month'
Week 2 of September
TH Positional or ordinal text:
'DDth "of " Month'
12Th of September
SP Spelled out number:
'MmSP Month Yyyysp'
Nine September
Two Thousand Eight
THSP or SPTH Spelled out positional or
ordinal number: 'hh24SpTh'
Fourteenth

Examples:
SQL> select c1 from test;
C1
---------
12-FEB-17
SQL> select to_char(c1,'Day "the "ddth "of" Month YYYY') as mytDate from test;
MYTDATE
--------------------------------------------------------------------------------
Sunday the 12th of February 2017

What is fm?
The names of days and months are automatically padded with spaces. These may be removed using a
modifier to the format mask called the fill mode (fm) operator.
Example:
SQL> select to_char(c1,'Day "the "ddth "of" Month YYYY') as mytDate from test;
MYTDATE
--------------------------------------------------------------------------------
SQL> select to_char(c1,'fmDay "the "ddth "of" Month YYYY') as mytDate from test;
MYTDATE
--------------------------------------------------------------------------------

Converting between calendars:
to_char(date, [format], [nls_parameter]),
There are two nls_parameters:
1. nls_date_language
2. nls_calendar

1. nls_date_language
The NLS_DATE_LANGUAGE parameter specifies the language for the day and the month names
produced by the TO_CHAR and TO_DATE functions.
2. nls_calendar
Many different calendar systems are in use throughout the world. NLS_CALENDAR specifies which
calendar system Oracle Database uses.

Examples:
SQL> select to_char(c1,'fmDay "of" fmMonth') as mydate from test;
MYDATE
----------------------------------------------------------------------------
Tuesday of March
SQL> select to_char(c1,'fmDay "of" fmMonth','nls_date_language=french') as mydate from test;
MYDATE
------------------------------------------------------------------------
Mardi of Mars
SQL> select to_char(c1,'fmDay "of" fmMonth','nls_date_language=persian') as mydate from test;
select to_char(c1,'fmDay "of" fmMonth','nls_date_language=persian') as mydate from test
*
ORA-12702: invalid NLS parameter string used in SQL function

How to use Persian Calendar in Oracle ?
SQL> select to_char(c1,'ddth "of" fmMonth "of" yyyy') as mydate from test;
MYDATE
----------------------------------------------------
21st of March of 2017
SQL> select to_char(c1,'ddth "of" fmMonth "of" yyyy','nls_calendar=persian') as mydate from test;
MYDATE
------------------------------------------------------------
01st of Farvardin of 1396
SQL> select to_char(c1,'yyyy/mm/dd','nls_calendar=persian') as mydate from test;
MYDATE
----------
1396/01/01

The necessity of using to_date function:
For inserting Date in Date data type columns (best practice)
Note: you could use only string formats for inserting Date data type in column based on
NLS_DATE_FORMAT parameter, otherwise use to_date function.

Examples:
SQL> select * from nls_session_parameters where parameter='NLS_DATE_FORMAT';
PARAMETER VALUE
-------------------- --------------------
NLS_DATE_FORMAT DD-MON-RR
SQL> insert into test values ('1980');
insert into test values ('1980')
*
ORA-01861: literal does not match format string
SQL> alter session set nls_date_format='yyyy';
Session altered.
SQL> insert into test values ('1990');
1 row created.

Examples cont’d:
SQL> select * from nls_session_parameters where parameter='NLS_DATE_FORMAT';
PARAMETER VALUE
------------------------------ --------------------
NLS_DATE_FORMAT yyyy
SQL> insert into test values (to_date('2016-aug-02','yyyy-mon-dd'));
1 row created.
SQL> insert into test values (to_date('2016','yyyy'));
1 row created.

What is fx?
fx specifies an exact match for string and the format mask. When the fx modifier is specified, character items
that do not exactly match the format mask yield an error.
to_date(string, [format], [nls_parameter])
SQL> insert into test values (to_date('25-DEC-10', 'dd-mon-yyyy'));
1 row created.
SQL> insert into test values (to_date('25-DEC-10', 'fxdd-mon-yyyy'));
insert into test values (to_date('25-DEC-10', 'fxdd-mon-yyyy'))
*
ORA-01862: the numeric value does not match the length of the format item

Simplifying the insertion of Persian Date:
SQL> insert into test values (to_date('1363/04/07 10:00','fxyyyy/mm/dd hh24:mi','nls_calendar=persian'));
1 row created.
SQL> select to_char(c1,'fmDay "the" ddth "of" Month yyyy') as mtdate from test;
MTDATE
--------------------------------------------------------------------------------
Thursday the 28th of June 1984
SQL> select to_char(c1,'fmDay "the" ddth "of" Month yyyy','nls_calendar=persian') as mtdate from test;
MTDATE
--------------------------------------------------------------------------------
Thursday the 7th of Tir 1363

Arithmetic on Date data type
Which arithmetic supported on Date data type:
Date1 – Date2 = Num1
Date1 + Num1 = Date2
Date1 = Date2 + Num1

Examples:
SQL> select sysdate - (sysdate + 1) as mydate from dual;
MYDATE
----------
-1
SQL> select sysdate + 1 as mydate from dual;
MYDATE
---------
14-FEB-17
As you can see, the standard unit in Oracle date arithmetic is one day.

Fractions of a day:
Precision Day Day Day
1 Day 1 1 1
1 Hour 1/24 1/24 0.0417
1 Min 1/(24x60) 1/1440 0.000694
1 Sec 1/(24x60x60) 1/86400 0.000011574

Examples:
SQL> select to_char(c1,'yyyy/mm/dd hh24:mi:ss') as mydate from test;
MYDATE
-------------------
2014/02/01 00:00:00
Add 5 minutes:
SQL> select to_char(c1 +(5/1440),'yyyy/mm/dd hh24:mi:ss') as mydate from test;
MYDATE
-------------------
2014/02/01 00:05:00

Examples cont’d:
The notation in the second column is most commonly used, because it is so much easier to read. Five
minutes is 5/(24x60), much easier than 5/1440 or 0.00347.
Subtracting 32 Second:
SQL> select to_char(c1-(32/(24*60*60)),'yyyy/mm/dd hh24:mi:ss') as mydate from test;
MYDATE
-------------------
2014/01/31 23:59:28

Oracle date arithmetic with intrinsic functions:
Date / Time Math Time Description
WHERE (date) > sysdate - 7/24; Past 7 hours
WHERE (date) > sysdate - 7; Past 7 days
WHERE (date) > sysdate - 7/1440; Past 7 minutes
13/24 13 hours
1/24/60/60 One second
5/24/60 Five minutes
5/24 Five hours
TRUNC(SYSDATE+1/24,'HH')
One hour starting with the next
hour

Single row functions
Some important functions:
MONTHS_BETWEEN
ADD_MONTHS
LAST_DAY
NEXT_DAY
SYSDATE
ROUND
TRUNC

MONTHS_BETWEEN:
The MONTHS_BETWEEN(date1, date2) function returns the number of months between two dates.
SQL> alter session set nls_calendar=persian;
Session altered.
SQL> select months_between('22-Bahman-1394','22-Ordibehesht-1310') as mydate from dual;
MYDATE
----------
1016.93548

ADD_MONTHS:
The ADD_MONTHS(date1, number of months) function returns the date resulting from adding a specified
number of months to a date.
SQL> select add_months('22-Bahman-1394',3) as mydate from dual;
MYDATE
-------------------
22 Ordibehesht 1395

LAST_DAY:
The LAST_DAY(date) function returns the last day of the month that the specified date falls into.
SQL> select last_day(to_date('09-Esfand-1395')) as mydate from dual;
MYDATE
-------------------
30 Esfand 1395
SQL> select last_day(to_date('09-Esfand-1394')) as mydate from dual;
MYDATE
-------------------
29 Esfand 1394

NEXT_DAY:
The NEXT_DAY(date1, day of the week) function returns the date on which the next specified day of the
week falls after the given date.
SQL> select to_char(to_date('09-Esfand-1395'),'fmDay "the" rr/mm/dd') as mydate from dual;
MYDATE
------------------
Monday the 95/12/9
SQL> select to_char(next_day('09-Esfand-1395','Friday'),'fmDay "the" rr/mm/dd') as mydate from dual;
MYDATE
-------------------
Friday the 95/12/13

SYSDATE:
The SYSDATE function takes no parameters and returns a date value that represents the current server
date and time.
SQL> select to_char(sysdate,'yyyy/mm/dd hh24:mi:ss') as mydate from dual;
MYDATE
-------------------
1395/11/26 10:38:24

ROUND:
The ROUND(date, date precision format) function round a given date value to the nearest date precision
format like day, month, or year.
SQL> select to_char(sysdate,'yyyy/mm/dd hh24:mi:ss') as currdate, to_char(round(sysdate,'mm'),'yyyy/m
m/dd hh24:mi:ss') as mydate from dual;
CURRDATE MYDATE
------------------- -------------------
2017/02/14 10:52:59 2017/02/01 00:00:00
SQL> select to_char(sysdate,'yyyy/mm/dd hh24:mi:ss') as currdate, to_char(round(sysdate,'hh'),'yyyy/m
CURRDATE MYDATE
------------------- -------------------
2017/02/14 10:53:28 2017/02/14 11:00:00

TRUNC:
The TRUNC(date, date precision format) truncate a given date value to the nearest date precision format
like day, month, or year.
SQL> select to_char(sysdate,'yyyy/mm/dd hh24:mi:ss') as currdate, to_char(trunc(sysdate,'mm'),'yyyy/m
CURRDATE MYDATE
------------------- -------------------
2017/02/14 10:57:49 2017/02/01 00:00:00
SQL> select to_char(sysdate,'yyyy/mm/dd hh24:mi:ss') as currdate, to_char(trunc(sysdate,'hh'),'yyyy/mm
/dd hh24:mi:ss') as mydate from dual;
CURRDATE MYDATE
------------------- -------------------
2017/02/14 10:58:07 2017/02/14 10:00:00

Oracle Globalization
NLS Parameters:
NLS (National Language Support) parameters determine the locale-specific behavior on both the client
and the server. NLS parameters can be specified in the following ways:
• As initialization parameters on the server
• As environment variables on the client
• With the ALTER SESSION statement
• In SQL functions

As initialization parameters on the server
You can include parameters in the initialization parameter file to specify a default session NLS
environment. These settings have no effect on the client side; they control only the server's behavior.
For example:
NLS_TERRITORY = "CZECH REPUBLIC"

As environment variables on the client
You can use NLS environment variables, which may be platform-dependent, to specify locale-dependent
behavior for the client and also to override the default values set for the session in the initialization param
eter file. For example:
Linux system:
export NLS_DATE_FORMAT="Day yyyy"
Windows system:
set NLS_DATE_FORMAT=yyyy/mm/dd hh24:mi:ss

With the ALTER SESSION statement:
You can use NLS parameters that are set in an ALTER SESSION statement to override the default
values that are set for the session in the initialization parameter file or set by the client with environment
variables.
ALTER SESSION SET NLS_SORT = AZERBAIJANI;

In SQL functions:
You can use NLS parameters explicitly to hardcode NLS behavior within a SQL function. This practice
overrides the default values that are set for the session in the initialization parameter file, client with
environment variables and ALTER SESSION statement.
For example:
TO_CHAR(hiredate, 'DD/MON/YYYY', ' nls_calendar=persian ')

Setting NLS Parameters and Their Priorities:
Priority Method
1 (highest) Explicitly set in SQL functions
2 Set by an ALTER SESSION statement
3 Set as an environment variable
4 Specified in the initialization parameter file
5 Default

Views to find current NLS settings:
• nls_database_parameters
• nls_instance_parameters
• nls_session_parameters
Note: NLS_CHARACTERSET, NLS_NCHAR_CHARACTERSET and NLS_RDBMS_VERSION, there
are only exist in the nls_database_parameter.

Find all valid CHARACTER SET,TERRITORY,LANGUAGE:
Simply with v$nls_valid_values
Example:
SQL> select * from v$nls_valid_values where lower(parameter) ='territory';
PARAMETER VALUE ISDEP
-------------------- ------------------------------ -------------
TERRITORY ECUADOR FALSE
TERRITORY PHILIPPINES FALSE
TERRITORY ALBANIA FALSE
98 rows selected.

Some important NLS parameters:
• NLS_TERRITORY
• NLS_DATE_FORMAT
• NLS_LANGUAGE (mentioned in section two)
• NLS_CALENDER (mentioned in section two)

NLS_TERRITORY:
The territory selection sets defaults for day and week numbering, credit and debit symbols, date formats,
decimal and group numeric separators, and currency symbols. Some of these can have profound effects
on the way your application software will behave.
Parameters American Germany
NLS_TERRITORY american germany
Decimal separator , .
Currency symbol $ €
First day of week Sunday Monday

NLS_TERRITORY:
Example:
alter session set NLS_TERRITORY='germany';
select to_char(8527,'L999G999') as myChar from dual;
€8.527
alter session set NLS_TERRITORY='america';
select to_char(8527,'L999G999') as myChar from dual;
$8,527

NLS_DATE_FORMAT:
The NLS_DATE_FORMAT parameter defines the default date format to use with the TO_CHAR and
TO_DATE functions. The NLS_TERRITORY parameter determines the default value of
NLS_DATE_FORMAT. The value of NLS_DATE_FORMAT can be any valid date format
mask. For example: NLS_DATE_FORMAT = "MM/DD/YYYY“
Country Description Example
Estonia dd.mm.yyyy 28.02.2003
Germany dd-mm-rr 28-02-03
Japan rr-mm-dd 03-02-28
UK dd-mon-rr 28-Feb-03
US dd-mon-rr 28-Feb-03

Date consideration in flashback
What is Flashback Technology ?
Oracle Flashback Technology is a group of Oracle Database features that let you view past states of data
base objects or to return database objects to a previous state without using point-in-time media recovery.
Oracle Flashback features use the Automatic Undo Management (AUM) system to obtain metadata and
historical data for transactions. They rely on undo data, which are records of the effects of individual tran
sactions. For example, if a user runs an UPDATE statement to change a salary from 1000 to 1100, then
Oracle Database stores the value 1000 in the undo data.

Using Oracle Flashback Query (SELECT AS OF)
To use Oracle Flashback Query, use a SELECT statement with an AS OF clause. Oracle Flashback
Query retrieves data as it existed at an earlier time. The query explicitly references a past time through a
time stamp or System Change Number (SCN). It returns committed data that was current at that point in
time.
Uses of Oracle Flashback Query include:
• Recovering lost data or undoing incorrect, committed changes.
For example, if you mistakenly delete or update rows, and then commit them, you can immediately undo
the mistake.
• Comparing current data with the corresponding data at an earlier time.
For example, you can run a daily report that shows the change in data from yesterday. You can compare
individual rows of table data or find intersections or unions of sets of rows.

Flashback Example:
SQL> select * from countries where country_name='Iran';
no rows selected
SQL> select to_char(sysdate,'rr/mm/dd hh24:mi:ss') as currdate from dual;
CURRDATE
-----------------
17/02/15 15:27:07
SQL> insert into countries values('IR','Iran',4);
1 row created.

Flashback Example cont’d:
SQL> select to_char(sysdate,'rr/mm/dd hh24:mi:ss') as currdate from dual;
CURRDATE
-----------------
17/02/15 15:28:29
CO COUNTRY_NAME REGION_ID
-- ---------------------------------------- ----------
IR Iran 4

Flashback Example cont’d:
SQL> select * from countries as of timestamp to_timestamp('17/02/15 15:27:07','rr/mm/dd hh24:mi:ss')
where country_name='Iran';
no rows selected
flashback table countries to timestamp to_timestamp('17/02/15 15:27:07','rr/mm/dd hh24:mi:ss');
Flashback succeeded.
no rows selected

Relative time:
If you specify a relative time by subtracting from the current time on the database host, the past time is re
calculated for each query. For example:
SQL> insert into countries values ('PO','Poland',1);
1 row created.
SQL> select * from countries As of timestamp (systimestamp - interval '1' minute) where country_name='
Poland';
CO COUNTRY_NAME REGION_ID
-- ---------------------------------------- ----------
PO Poland 1

Arguments which could be passed to relevant flashback:
select * from countries As of timestamp (systimestamp - interval '1' <argument>);
Arguments
Year
Month
Day
Hour
Minute
Second

Relative or Exact ?
Exact example:
select * from countries As of timestamp to_timestamp('17/02/18 10:49:12', 'rr/mm/dd hh24:mi:ss');
Relative example:
select * from countries As of timestamp (systimestamp - interval '1' minute);
Method Simplicity Accuracy
Exact No Yes
Relative Yes No

References
• https://docs.oracle.com/cd/E11882_01/server.112/e10729/ch4datetime.htm#NLSPG004
• https://docs.oracle.com/cd/E18283_01/server.112/e10729/ch3globenv.htm
• https://docs.oracle.com/cd/E11882_01/appdev.112/e41502/adfns_flashback.htm#ADFNS1008

Question and Answer
https://ir.linkedin.com/in/masoud-haji-hassan-pour
Masoud Haji Hassan Pour
mas.Hassanpour@gmail.com
Thanks
for your attention

Date data type and Globalization in Oracle

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