how to calculate number of working days in pure sql [duplicate] - sql

Question

I have two date columns and trying to measure days between the two dates excluding weekends. I'm getting a negative number and need help solving.
Table
CalendarDate DayNumber FirstAssgn FirstCnt DayNumber2 Id BusinessDays
5/21/2017 Sunday 5/21/17 5/21/17 Sunday 1 -1
Query:
TRUNC(TO_DATE(A.FIRST_CONTACT_DT, 'DD/MM/YYYY')) - TRUNC(TO_DATE(A.FIRST_ASSGN_DT, 'DD/MM/YYYY'))
- ((((TRUNC(A.FIRST_CONTACT_DT,'D'))-(TRUNC(A.FIRST_ASSGN_DT,'D')))/7)*2)
- (CASE WHEN TO_CHAR(A.FIRST_ASSGN_DT,'DY','nls_date_language=english') ='SUN' THEN 1 ELSE 0 END)
- (CASE WHEN TO_CHAR(A.FIRST_CONTACT_DT,'DY','nls_date_language=english')='SAT' THEN 1 ELSE 0 END)
- (SELECT COUNT(1) FROM HUM.CALENDAR CAL
WHERE 1=1
AND CAL.CALENDAR_DATE >= A.FIRST_ASSGN_DT
AND CAL.CALENDAR_DATE < A.FIRST_CONTACT_DT
--BETWEEN A.FIRST_ASSGN_DT AND A.FIRST_CONTACT_DT
AND CAL.GRH_HOLIDAY_IND = 'Y'
) AS Business_Days
Looks like below piece needs editing...
- (CASE WHEN TO_CHAR(A.FIRST_ASSGN_DT,'DY','nls_date_language=english')='SUN' THEN 1 ELSE 0 END)

Answer 1

Adapted from my answer here:
Get the number of days between the Mondays of both weeks (using TRUNC( datevalue, 'IW' ) as an NLS_LANGUAGE independent method of finding the Monday of the week) then add the day of the week (Monday = 1, Tuesday = 2, etc., to a maximum of 5 to ignore weekends) for the end date and subtract the day of the week for the start date. Like this:
SELECT ( TRUNC( end_date, 'IW' ) - TRUNC( start_date, 'IW' ) ) * 5 / 7
+ LEAST( end_date - TRUNC( end_date, 'IW' ) + 1, 5 )
- LEAST( start_date - TRUNC( start_date, 'IW' ) + 1, 5 )
AS WeekDaysDifference
FROM your_table

Answer 2

With RANGE_TEMP as (
SELECT
STARTPERIOD start_date,
ENDPERIOD end_date
FROM
TABLE_DATA -- YOUR TABLE WITH ALL DATA DATE
), DATE_TEMP AS (
SELECT
(start_date + LEVEL) DATE_ALL
FROM
RANGE_TEMP
CONNECT BY LEVEL <= (end_date - start_date)
), WORK_TMP as (
SELECT
COUNT(DATE_ALL) WORK_DATE
FROM
DATE_TEMP
WHERE
TO_CHAR(DATE_ALL,'D', 'NLS_DATE_LANGUAGE=ENGLISH') NOT IN ('1','7')
), BUSINESS_TMP as (
SELECT
COUNT(DATE_ALL) BUSINESS_DATE
FROM
DATE_TEMP
WHERE
TO_CHAR(DATE_ALL,'D', 'NLS_DATE_LANGUAGE=ENGLISH') IN ('1','7')
)
SELECT
L.WORK_DATE,
H.BUSINESS_DATE
FROM
BUSINESS_TMP H,
WORK_TMP L
;