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Oracle comparing dates : dates, oracle, date comparison in oracle pl/sql

globinch-sql-plsql — Wed, 19 Nov 2008 09:08:00 +0000

How to compare dates in oracle?There are a number of ways you can compare two dates in oracle to check which is greater or which is small.This is particularly useful when we do operations based on certain date conditions.This is used along with to_date and other date functions.
The following example illustrates the date comparison in Oracle pl/sql.

SQL> SET SERVEROUTPUT ON;
SQL>
SQL> -- Created on 11/19/2008 by Globinch PLSQLTIPS
SQL> declare
-- Local variables here
test_Date DATE;
begin
   --- Initialize the test date a future date.
      test_Date := to_date('12/12/2008','DD/MM/YYYY');
      if test_date>sysdate then
         dbms_output.put_line('The date :' || test_Date||': This is a future date!');
      end if;
      ----Now subtract 60 days from the test date
      test_Date := test_Date - 60;
      if test_date

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Oracle Dates and Times |SYSDATE|CURRENT_TIMESTAMP |SYSTIMESTAMP |DBTIMEZONE |LOCALTIMESTAMP

globinch-sql-plsql — Tue, 18 Nov 2008 13:32:00 +0000

The DATE type is stored in a special internal format that includes not just the month, day, and year, but also the hour, minute, and second.There are a number of key words and functions provided by oracle to use the date and timestamp data types in much flexible ways.

TIMESTAMP datatype
In addition to the DATE data type Oracle has TIMESTAMP data type which stores all the information that the DATE data type stores, but also includes fractional seconds.

CURRENT_TIMESTAMP will give the current time with all details.
DBTIMEZONE will give the database timezone set.

Read the below articles to know more about time and date features in oracle
oracle to_date | Oracle/PLSQL: To_Date Function
oracle date difference | date difference in sql an…
DATE Data type in Oracle|Oracle Dates and Times|Da…
Formatting date in SQL (Oracle) -Simple date forma…

Examples for all the above features give below.

The current Time :

SQL> select to_char(sysdate, 'Dy DD-Mon-YYYY HH24:MI:SS') as "Now" from dual;
Now
Tue 18-Nov-2008 18:47:25

TIMESTAMP Example

SQL> SELECT CAST(sysdate AS TIMESTAMP) "Date" FROM dual;
Date
18-NOV-08 06.50.41.000000 PM
SQL>

DATE and Time formating Example

SQL> SELECT TO_CHAR(sysdate,'Dy MM/DD/YYYY HH24:MI:SS') "Current Time" from dual;
Current Time
Tue 11/18/2008 18:51:49
SQL>

SYSTIMESTAMP Example

SQL> SELECT TO_CHAR(SYSTIMESTAMP,'Dy MM/DD/YYYY HH24:MI:SS') "Current Time" from dual;
Current Time
Tue 11/18/2008 18:52:39
SQL>

CURRENT_TIMESTAMP Example

SQL> SELECT  CURRENT_TIMESTAMP FROM dual;
CURRENT_TIMESTAMP
18-NOV-08 06.53.42.628000 PM +05:30
SQL>

DBTIMEZONE Example

SQL> SELECT DBTIMEZONE FROM dual;
DBTIMEZONE
+00:00
SQL>

LOCALTIMESTAMP and CURRENT_TIMESTAMP Example

SQL> SELECT CURRENT_TIMESTAMP,  LOCALTIMESTAMP FROM dual;
CURRENT_TIMESTAMP                                 LOCALTIMESTAMP
18-NOV-08 06.55.55.067000 PM +05:30               18-NOV-08 06.55.55.067000 PM

SQL>

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oracle to_date | Oracle/PLSQL: To_Date Function

globinch-sql-plsql — Tue, 18 Nov 2008 12:16:00 +0000

The purpose of TO_DATE in Oracle pl/sql is to convert char of CHAR, VARCHAR2, NCHAR, or NVARCHAR2 data type to a value of DATE datatype.Or more generically the Oracle to_date function is used to change a test string (or variable) into an internal date format.

Syntax
to_date( stringDate, [ format_mask ], [ nls_param ] )

Where
stringDate : is the string to convert to date
format_mask : is the format that will be used to convert stringDate to a date.
nls_param : is the nls language used to convert stringDate to a date.

Examples:

SQL> select to_date('JAN/12/2009' ,'MON-DD-YYYY HH24:MI:SS') THE_DATE from dual;
THE_DATE
1/12/2009

SQL> select to_date('20080312','YYYYMMDD') from dual;

TO_DATE('20080312','YYYYMMDD')
3/12/2008
SQL> select to_date('20080312','YYYYDDMM') from dual;

TO_DATE('20080312','YYYYDDMM')
12/3/2008

SQL> select to_date('2006/11/14 18', 'yyyy/mm/dd hh24') from dual;

TO_DATE('2006/11/1418','YYYY/M
11/14/2006 6:00:00 PM

SQL> SELECT TO_DATE('January 15, 1989, 11:00 A.M.', 'Month dd, YYYY, HH:MI A.M.','NLS_DATE_LANGUAGE = American')FROM DUAL;
TO_DATE('JANUARY15,1989,11:00A
1/15/1989 11:00:00 AM
SQL>

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Oracle date difference | date difference in sql and PL/SQL

globinch-sql-plsql — Thu, 13 Nov 2008 07:18:00 +0000

Oracle maintains the SYSDATE pseudo-column to show the current system date and time.
How to find the difference between two dates in Oracle? The following examples gives different useful methods to do this.

With Oracle Dates, this is simple by subtracting the dates and do some minor modification to get get Days/Hours/Minutes/Seconds between the dates.

See the following example.

SQL> set serveroutput on;
SQL> declare
   today       date;
   nextday       date;
begin
  today := sysdate;<
   --Add 1 day to sysdate
   nextday := sysdate+1;
   dbms_output.put_line('>> Tomorrow is ' || (nextday-today) || ' day ahead of today' );
   dbms_output.put_line('>> Tomorrow is ' || (nextday-today)*24 || ' hours ahead of today ' );
   dbms_output.put_line('>> Tomorrow is ' || (nextday-today)*24*60 || '  minutes ahead of today' );
   dbms_output.put_line('>> Tomorrow is ' || (nextday-today)*24*60*60 || ' seconds ahead of today');
  end;
 /

 >> Tomorrow is 1 day ahead of today
 >> Tomorrow is 24 hours ahead of today
 >> Tomorrow is 1440  minutes ahead of today
 >> Tomorrow is 86400 seconds ahead of today

PL/SQL procedure successfully completed.

Adding 1 to SYSDATE will advance the date by 1 day. By adding fractions to sysdate we can advance by hours,minutes and seconds.

Current time :SYSDATE
Tomorrow :SYSDATE+1
One hour from now :SYSDATE + 1/24
One minute from now :SYSDATE + 1/1440
Five second from now :SYSDATE + 5/86400

See the example below,

SQL> set serveroutput on;
SQL>  declare
  begin
     dbms_output.put_line('>> Current Time        :' || TO_CHAR(SYSDATE,'DD-MON-YYYY HH24:MI:SS'));
    dbms_output.put_line('>> Tomorrow is         :' || TO_CHAR((SYSDATE + 1),'DD-MON-YYYY HH24:MI:SS'));
    dbms_output.put_line('>> One hour from now   :' || TO_CHAR((SYSDATE + 1/24),'DD-MON-YYYY HH24:MI:SS'));
    dbms_output.put_line('>> One minute from now :' || TO_CHAR((SYSDATE + 1/1440),'DD-MON-YYYY HH24:MI:SS'));
    dbms_output.put_line('>> Five second from now: ' || TO_CHAR((SYSDATE + 5/86400),'DD-MON-YYYY HH24:MI:SS'));
end;

>> Current Time        :13-NOV-2008 12:45:29
>> Tomorrow is         :14-NOV-2008 12:45:29
>> One hour from now   :13-NOV-2008 13:45:29
>> One minute from now :13-NOV-2008 12:46:29
>> Five second from now: 13-NOV-2008 12:45:34
PL/SQL procedure successfully completed.
SQL>

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DATE Data type in Oracle|Oracle Dates and Times|Dates in OracleDATE Data type in Oracle|Oracle Dates and Times|Dates in Oracle

globinch-sql-plsql — Thu, 13 Nov 2008 06:35:00 +0000

In Oracle Date data is stored in fixed-length fields of seven bytes each, corresponding to century, year, month, day, hour, minute, and second. (Also Read Formatting date in SQL (Oracle) -Simple date forma…) .The date and timestamp types and the formatting functions could be the most used functions of pl/sql.

The standard Oracle date format is ‘DD-MON-YY’ for example ‘13-Nov-08′.

How to change this default date format for an oracle instance ?

NLS_DATE_FORMAT specifies the default date format to use with the TO_CHAR and TO_DATE functions.
This is specified oin the in the parameter file(init.ora).

For example
NLS_DATE_FORMAT = “MM/DD/YYYY”

The default value of this parameter is determined by NLS_TERRITORY.
During a user session user can change this with the ALTER SESSION statement.

For example


alter session set nls_date_format='DD-MON-YYYY HH24:MI:SS'

How to enter dates that are not in standard Oracle date format?

Use the TO_DATE function with a format mask,For example

SQL> select unique TO_DATE ('November 13, 1992', 'MONTH DD, YYYY') mydate from tab;
MYDATE
11/13/1992
SQL>

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Formatting date in SQL (Oracle) -Simple date formatting

globinch-sql-plsql — Tue, 28 Oct 2008 11:14:00 +0000

Here is few simple SQL date formatting examples that can be useful while displaying dates in different formats.There are a number of formatting techniques available for dates and timestamps.
1. DD:MONTH:YYYY HH24:MI:SS format

SQL> select distinct to_char(sysdate,'DD:MONTH:YYYY hh12:MI:ss') TIME_NOW from tab;

TIME_NOW
28:OCTOBER  :2008 04:37:12

2. Year in strings

SQ> select distinct to_char(sysdate,'DD-MONTH-YEAR hh12:mm:ss') today from tab;
TODAY
28-OCTOBER  -TWO THOUSAND EIGHT 04:10:40

3. Day and date as string

SQL> select distinct to_char(sysdate,'DAY DD--MONTH--YEAR hh12:mm:ss') today from tab;
TODAY
TUESDAY   28--OCTOBER  --TWO THOUSAND EIGHT 04:10:09

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Oracle timestamp format milliseconds| Oracle Date format

Oracle Data types

globinch-sql-plsql — Tue, 05 Jun 2007 13:59:00 +0000

Datatypes

Every constant and variable has a data type ,which specifies the storage format. It also specifies the constraints ad valid range of values.
We can generalize the different types as follows
scalar type :This type has no internal components.
composite :This type has internal components that can be manipulated individually.
reference :This type holds pointers, that designate other program items.
LOB :This type holds values called lob locators, that specify the location of large objects

Scalar type	Subtypes	Composite type	Reference type	LOB type
BINARY_INTEGER	NATURAL	RECORD TABLE VARRAY	REF CURSOR REF object_Type	BFILE BLOB CLOB NCLOB
	POSITIVE
	NATURALN
	POSITIVEN
	SIGNTYPE
PLS_INTEGER
NUMBER	INT
	INTEGER
	SMALLINT
	DEC
	DECIMAL
	NUMERIC
	DOUBLE PRECISION
	FLOAT
	BINARY_DOUBLE
	BINARY_FLOAT
CHAR	CHARACTER
NCHAR
VARCHAR2	STRING
	VARCHAR
NVARCHAR2
RAW
ROWID
UROWID
BOOLEAN
DATE

Data type defintion	PL/SQL	SQL
CHAR()	32,767 chars	2,000 chars
NCHAR()	32,767 bytes	2,000 bytes
LONG	32,760 bytes	2GB
VARCHAR2()	32,767 chars	4,000 chars
NVARCHAR2()	32,767 bytes	4,000 bytes
CHARACTER	2,000 chars	2,000 chars
STRING()	32,767 bytes	N/A
VARCHAR	32,767 bytes	N/A
*Integer*
BINARY_INTEGER (same as PLS_INTEGER in 10g)	32 bit	N/A
PLS_INTEGER	32 bit	N/A
*Floating Point*
NUMBER	38 chars	38 chars
*Fixed Point*
NUMBER( ,)	38 chars	38 chars
*Non-negative Integers*
NATURAL	32 bit	N/A
POSITIVE	32 bit	N/A
*Not Nullable Non-negative Integers*
NATURALN	32 bit	N/A
POSITIVEN	32 bit	N/A
*Restricted*
SIGNTYPE	-1, 0, +1	N/A
Integers with up to 38 decimal digits
INT	38	38
INTEGER	38	38
SMALLINT	38	38
*Fixed point numbers up to 38 decimal digits*
DEC( ,)	38	38
DECIMAL( ,)	38	38
NUMERIC( ,)	38	38
*Floating point numbers up to 126 binary digits*
DOUBLE PRECISION()	126	126
FLOAT()	126	126
REAL	63 bin.digits	63 bin.digits
*Floating point numbers using native machine arithmetic*
BINARY_DOUBLE	64 bit	64 bit
BINARY_FLOAT	32 bit	32 bit