Working with dates in Oracle SQL

Question

I am very new when it comes to using SQL and what I am attempting to do is select the waterUsage and electrcityUsage using only the month and year and select the waterUsage and

Answer 1

Assuming that BILLINGDATE is a DATE column:

I recommend avoiding the use of the TO_CHAR or EXTRACT function in a case like this, as they're likely to force a full table scan - perhaps not an issue for small databases and tables, but perhaps very important when querying a large table. Instead I suggest getting used to using a BETWEEN comparison for handling date ranges - something similar to the following:

SELECT ELECTRICITYUSAGE, WATERUSAGE
  FROM MONTHLYBILL
  WHERE ACCOUNTNUMBER = '211' AND
        BILLING_DATE BETWEEN TO_DATE('01-DEC-2012 00:00:00', 'DD-MON-YYYY HH24:MI:SS')
                         AND TO_DATE('31-DEC-2012 23:59:59', 'DD-MON-YYYY HH24:MI:SS')

It's important to remember that in Oracle a DATE column is actually a timestamp and so there is always a date and a time component to it (accurate only down to seconds, not milli- or micro-seconds), so you always need to take the hours/minutes/seconds into account when dealing with Oracle DATEs.

Best of luck.