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Comparing Dates in Oracle SQL

People also ask

Can we compare two dates in Oracle?

This will enable you to do a string comparison. However, you're not doing a string comparison; you're doing a date comparison. You should transform your string into a date. Either by using the built-in TO_DATE() function, or a date literal.

Can you compare dates in SQL?

We can compare dates using Comparison Operators in SQL like, = (Equals), < (Less than), > (Greater than), <= (Less than Equal), >= (Greater than Equal), <> (Not Equal), etc.

How can I compare current date and date in Oracle?

DECLARE v_exit_date DATE; --Let's assume exit_date from the database is today's date '15-APR-10' BEGIN SELECT exit_date INTO v_exit_date FROM TABLE_1 WHERE student_id = 3020; IF v_exit_date = sysdate THEN dbms_output. putline ('Dates are equal'); ELSE dbms_output.

How does SQL Developer compare dates?

SQL Date comparison is most used statement for DBA or developers. If you will compare any column with a DATE format, related column and data should be DATE datatype, namely SQL date comparison should be between DATE to DATE format as follows.


31-DEC-95 isn't a string, nor is 20-JUN-94. They're numbers with some extra stuff added on the end. This should be '31-DEC-95' or '20-JUN-94' - note the single quote, '. This will enable you to do a string comparison.

However, you're not doing a string comparison; you're doing a date comparison. You should transform your string into a date. Either by using the built-in TO_DATE() function, or a date literal.

TO_DATE()

select employee_id
  from employee
 where employee_date_hired > to_date('31-DEC-95','DD-MON-YY')

This method has a few unnecessary pitfalls

  • As a_horse_with_no_name noted in the comments, DEC, doesn't necessarily mean December. It depends on your NLS_DATE_LANGUAGE and NLS_DATE_FORMAT settings. To ensure that your comparison with work in any locale you can use the datetime format model MM instead
  • The year '95 is inexact. You know you mean 1995, but what if it was '50, is that 1950 or 2050? It's always best to be explicit
select employee_id
  from employee
 where employee_date_hired > to_date('31-12-1995','DD-MM-YYYY')

Date literals

A date literal is part of the ANSI standard, which means you don't have to use an Oracle specific function. When using a literal you must specify your date in the format YYYY-MM-DD and you cannot include a time element.

select employee_id
  from employee
 where employee_date_hired > date '1995-12-31'

Remember that the Oracle date datatype includes a time elemement, so the date without a time portion is equivalent to 1995-12-31 00:00:00.

If you want to include a time portion then you'd have to use a timestamp literal, which takes the format YYYY-MM-DD HH24:MI:SS[.FF0-9]

select employee_id
  from employee
 where employee_date_hired > timestamp '1995-12-31 12:31:02'

Further information

NLS_DATE_LANGUAGE is derived from NLS_LANGUAGE and NLS_DATE_FORMAT is derived from NLS_TERRITORY. These are set when you initially created the database but they can be altered by changing your inialization parameters file - only if really required - or at the session level by using the ALTER SESSION syntax. For instance:

alter session set nls_date_format = 'DD.MM.YYYY HH24:MI:SS';

This means:

  • DD numeric day of the month, 1 - 31
  • MM numeric month of the year, 01 - 12 ( January is 01 )
  • YYYY 4 digit year - in my opinion this is always better than a 2 digit year YY as there is no confusion with what century you're referring to.
  • HH24 hour of the day, 0 - 23
  • MI minute of the hour, 0 - 59
  • SS second of the minute, 0-59

You can find out your current language and date language settings by querying V$NLS_PARAMETERSs and the full gamut of valid values by querying V$NLS_VALID_VALUES.

Further reading

  • Format models

Incidentally, if you want the count(*) you need to group by employee_id

select employee_id, count(*)
  from employee
 where employee_date_hired > date '1995-12-31'
 group by employee_id

This gives you the count per employee_id.


Conclusion,

to_char works in its own way

So,

Always use this format YYYY-MM-DD for comparison instead of MM-DD-YY or DD-MM-YYYY or any other format


You can use trunc and to_date as follows:

select TO_CHAR (g.FECHA, 'DD-MM-YYYY HH24:MI:SS') fecha_salida, g.NUMERO_GUIA, g.BOD_ORIGEN, g.TIPO_GUIA, dg.DOC_NUMERO, dg.* 
from ils_det_guia dg, ils_guia g
where dg.NUMERO_GUIA = g.NUMERO_GUIA and dg.TIPO_GUIA = g.TIPO_GUIA and dg.BOD_ORIGEN = g.BOD_ORIGEN
and dg.LAB_CODIGO = 56 
and trunc(g.FECHA) > to_date('01/02/15','DD/MM/YY')
order by g.FECHA;

from your query:

Select employee_id, count(*) From Employee 
Where to_char(employee_date_hired, 'DD-MON-YY') > '31-DEC-95' 

i think its not to display the number of employees that are hired after June 20, 1994. if you want show number of employees, you can use:

Select count(*) From Employee 
Where to_char(employee_date_hired, 'YYYMMMDDD') > 19940620 

I think for best practice to compare dates you can use:

employee_date_hired > TO_DATE('20-06-1994', 'DD-MM-YYYY');
or
to_char(employee_date_hired, 'YYYMMMDDD') > 19940620;