Oracle SQL comparison of DATEs returns wrong result

Question

I have REPORTDATE column in database (DATETIME) type. I want to extract only DATE value from the DATETIME, then to do COUNT

Answer 1

WHERE to_char(REPORTDATE, 'DD.MM.YYYY')>'09.11.2013'

You are comparing two STRINGS. You need to compare the DATEs. As I already said in the other answer here, you need to leave the date as it is for DATE calculations. TO_CHAR is for display, and TO_DATE is to convert a string literal into DATE.

SELECT TO_CHAR(REPORTDATE, 'DD.MM.YYYY'),
  COUNT(*)
FROM TABLE
WHERE REPORTDATE > TO_DATE('09.11.2013', 'DD.MM.YYYY')
GROUP BY TO_CHAR(REPORTDATE, 'DD.MM.YYYY') 

Also, REPORTDATE is a DATE column, hence it will have datetime element. So, if you want to exclude the time element while comparing, you need to use TRUNC

WHERE TRUNC(REPORTDATE) > TO_DATE('09.11.2013', 'DD.MM.YYYY')

However, applying TRUNC on the date column would suppress any regular index on that column. From performance point of view, better use a Date range condition.

For example,

WHERE REPORTDATE
BETWEEN 
        TO_DATE('09.11.2013', 'DD.MM.YYYY')
AND     
        TO_DATE('09.11.2013', 'DD.MM.YYYY') +1