10 Most Important Date / Time related queries

10 Most Important Date / Time related queries

1. Get the first day of the month

Quickly returns the first day of current month. Instead of current month you want to find first day of month where a date falls, replace SYSDATE with any date column/value.

SELECT TRUNC (SYSDATE, 'MONTH') "First day of current month"     FROM DUAL;

2. Get the last day of the month

This query is similar to above but returns last day of current month. One thing worth noting is that it automatically takes care of leap year. So if you have 29 days in Feb, it will return 29/2. Also similar to above query replace SYSDATE with any other date column/value to find last day of that particular month.

SELECT TRUNC (LAST_DAY (SYSDATE)) "Last day of current month"     FROM DUAL;

3. Get the first day of the Year

First day of year is always 1-Jan. This query can be use in stored procedure where you quickly want first day of year for some calculation.

SELECT TRUNC (SYSDATE, 'YEAR') "Year First Day" FROM DUAL;

4. Get the last day of the year

Similar to above query. Instead of first day this query returns last day of current year.

SELECT ADD_MONTHS (TRUNC (SYSDATE, 'YEAR'), 12) - 1 "Year Last Day" FROM DUAL

5. Get number of days in current month

Now this is useful. This query returns number of days in current month. You can change SYSDATE with any date/value to know number of days in that month.

SELECT CAST (TO_CHAR (LAST_DAY (SYSDATE), 'dd') AS INT) number_of_days   FROM DUAL;

6. Get number of days left in current month

Below query calculates number of days left in current month.

SELECT SYSDATE,        LAST_DAY (SYSDATE) "Last",        LAST_DAY (SYSDATE) - SYSDATE "Days left"   FROM DUAL;

7. Get number of days between two dates

Use this query to get difference between two dates in number of days.

SELECT ROUND ( (MONTHS_BETWEEN ('01-Feb-2014', '01-Mar-2012') * 30), 0)           num_of_days   FROM DUAL; OR SELECT TRUNC(sysdate) - TRUNC(e.hire_date) FROM employees;

Use second query if you need to find number of days since some specific date. In this example number of days since any employee is hired.

8. Display each months start and end date upto last month of the year

This clever query displays start date and end date of each month in current year. You might want to use this for certain types of calculations.

SELECT ADD_MONTHS (TRUNC (SYSDATE, 'MONTH'), i) start_date,        TRUNC (LAST_DAY (ADD_MONTHS (SYSDATE, i))) end_date   FROM XMLTABLE (           'for $i in 0 to xs:int(D) return $i'           PASSING XMLELEMENT (                      d,                      FLOOR (                         MONTHS_BETWEEN (                            ADD_MONTHS (TRUNC (SYSDATE, 'YEAR') - 1, 12),                            SYSDATE)))           COLUMNS i INTEGER PATH '.');

9. Get number of seconds passed since today (since 00:00 hr)

SELECT (SYSDATE - TRUNC (SYSDATE)) * 24 * 60 * 60 num_of_sec_since_morning   FROM DUAL;

10. Get number of seconds left today (till 23:59:59 hr)

SELECT (TRUNC (SYSDATE+1) - SYSDATE) * 24 * 60 * 60 num_of_sec_left   FROM DUAL;