I may/maynot have Mar-2015 qvd. I am able to do conditional load like this:
IF (NOT isNull(qvdCreateTime('QVDs\Mar-2015'))) THEN
QUALIFY *;
UNQUALIFY Id;
PreviousMonthData:
LOAD
Id,
Name,
Price AS PreviousMonthPrice,
MetaData1 AS PreviousMonthMetaData1,
MetaData2 AS PreviousMonthMetaData2
FROM
[QVDs\Mar-2015.qvd]
(qvd);
UNQUALIFY *;
END IF
This is my second qvd.
CurrentMonthData:
LEFT JOIN (PreviousMonthData)
LOAD
Id,
Name,
Price AS CurrentMonthPrice,
LastPriceChangedON
MetaData1 AS CurrentMonthMetaData1,
MetaData2 AS CurrentMonthMetaData2
FROM
[QVDs\Apr-2015.qvd]
(qvd);
This is my Final Table:
FinalTable:
LOAD *,
IF (PreviousMonthMetaData1 <> CurrentMonthMetaData1 or PreviousMonthMetaData2 <> CurrentMonthMetaData2,' Changed', 'Not Changed') as Status
Resident PreviousMonthData;
DROP TABLE PreviousMonthData;
The problem here is if my first qvd does not exist, my second qvd load fails as it does not find PreviousMonthData table in the LEFT JOIN sentence. I can write something like this:
if isnull(TableNumber('PreviousMonthData')) then
PreviousMonthData:
LOAD
Id,
Name,
Price AS CurrentMonthPrice,
LastPriceChangedON
MetaData1 AS CurrentMonthMetaData1,
MetaData2 AS CurrentMonthMetaData2
FROM
[QVDs\Apr-2015.qvd]
(qvd);
ELSE
CurrentMonthData:
LEFT JOIN (PreviousMonthData)
LOAD
Id,
Name,
Price AS CurrentMonthPrice,
LastPriceChangedON
MetaData1 AS CurrentMonthMetaData1,
MetaData2 AS CurrentMonthMetaData2
FROM
[QVDs\Apr-2015.qvd]
(qvd);
end if
But this makes it hard to maintain as i have to make changes at 2 places when i add/remove a field.
Also in my final table i have to do the same thing as if there is no PreviousMonthData table then create fake column in the else statement.
Is there a better solution to this?
