Merging 2 datesets with overlap

[radhikaa4]

Hello,

I have 2 datasets and I would like to create 3rd dataset 

Dataset #1

patientID	date	volume
4444	1/2/2014	45
4444	1/3/2014	50
4444	1/4/2014	12
4444	1/5/2014	33
4444	1/6/2014	12
3233	1/6/2015	66
3233	1/7/2015	35
3233	1/9/2015	23

Dataset #2

patientID	date	flag
4444	1/4/2014	1
3233	1/7/2015	1

Want dataset #3

patientID	date	volume	flag
4444	1/2/2014	45
4444	1/3/2014	50
4444	1/4/2014	12	1
4444	1/5/2014	33
4444	1/6/2014	12
3233	1/6/2015	66
3233	1/7/2015	35	1
3233	1/9/2015	23

I tried the following

PROC SQL;

SELECT bb.*, cc.flag

FROM a.dataset_1 bb LEFT JOIN a.dataset_2 cc on bb.patientID = cc.patientID;

QUIT;

But it doesn't work or shows "flag = 1" for all the records. I also tried full outer join etc. 

Thanks

[Reeza]

Add a condition to join on date as well.

and bb.date=cc.date