有什么方法可以使用DB2 SQL在表Workorder中查找重叠时间？

Question

I want to make a report using DB2 SQL that will show the list of duration (hours) between 15th and 17th May. The current list look like this:

click here to view the list

As you can see, from WO-391296 (second row) it has overlapping time in ACTSTART and ACTFINISH .

I've already tried the Overlaps function. This is my query :

SELECT
    *
FROM
    workorder a,
    workorder b
WHERE
    a.wonum <> b.WONUM
    AND (a.ACTSTART, a.ACTFINISH) OVERLAPS (b.ACTSTART, b.ACTFINISH)
    AND DATE(a.ACTSTART) = '2019-05-15'
    AND DATE(a.ACTFINISH) = '2019-05-17'
    AND a.assetnum = 'A0000004'
    AND DATE(b.ACTSTART) = '2019-05-15'
    AND DATE(b.ACTFINISH) = '2019-05-17'
    AND b.assetnum = 'A0000004' ;

But it doesn't work and just giving me the error message.:

SQL Error [42601]: An unexpected token "OVERLAPS" was found following "TSTART, a.ACTFINISH)". Expected tokens may include: "IN".. SQLCODE=-104, SQLSTATE=42601, DRIVER=3.64.114

Here's my actual full query :

SELECT assetnum, wonum, worktype, actstart, actfinish, 
    (DAY(ACTFINISH-ACTSTART)*24 + HOUR(ACTFINISH-ACTSTART)) + FLOAT(MINUTE(ACTFINISH-ACTSTART))/60 AS wotime 
FROM ( 
    SELECT assetnum, wonum, WORKTYPE, ACTSTART, 
        (CASE WHEN ACTFINISH IS NULL THEN '2019-05-17-24.00.00' ELSE ACTFINISH END) AS ACTFINISH 
    FROM workorder ast 
    WHERE istask=0 AND siteid = 'SBY' AND WORKTYPE = 'CM' AND
        (ast.assetnum = 'A0000004' or 
         assetnum in (select distinct assetnum from asset ast where ast.parent = 'A0000004') or 
         assetnum in (select distinct assetnum from asset ast where ast.parent 
                  in (select distinct assetnum from asset ast where ast.parent = 'A0000004'))) AND 
        ( 
            (status IN ('COMP', 'CONFIRM', 'CLOSE') AND 
            (date(ACTFINISH) BETWEEN '2019-05-15' and '2019-05-17')) OR 
            (status IN ('INPRG', 'COMP', 'CONFIRM', 'CLOSE') AND 
            (date(ACTSTART) <= '2019-05-17' AND (date(ACTFINISH) > '2019-05-17' OR ACTFINISH IS null))) 
        ) 
); 

The actual total duration of this list is 6 hours which is wrong , because I don't want to SUM the overlapping time.

So, the final result must be 3.5 hours (without WO-391296 ).

Answer 1

2 Intervals overlap if:
start of the 1-st is <= of end of the 2-nd
and
start of the 2-nd is <= of end of the 1-st

create or replace function overlaps_dates (a_from date, a_to date, b_from date, b_to date)
returns int
deterministic
no external action
contains sql
return case when min(a_from, a_to) <= max(b_from, b_to) and min(b_from, b_to) <= max(a_from, a_to) then 1 else 0 end;