Hi all,   I am hoping you can help me! **Please help!!!!** 🙏 I am in SAS and I have datasets A and B with different measurements (relating to patient's health) as follows:   Dataset A ID            Date               measurement_a 1          20JUN2013                52.3 1          12JUL2013                 65.6 1          28NOV2014                37.4 1          02DEC2014                61.3 1          22SEP2015                40.5 1         15OCT2015                 60.5 2         03JUN2011                 46.5 2         19JUL2011                  54.1 2         29OCT2012                 53.6 Dataset B ID            Date                  measurement_b 1          21MAR2007                  43 1          13JUL2007                   45 1           07APR2009                 47 1           14MAY2009                 46 1           16FEB2012                  42 1           27AUG2012                 53 1           12DEC2012                 58 1           20JUN2013                  56 1           10DEC2013                  53 1           23MAY2014                  49 1           17SEP2014                  44 1           23SEP2015                  40 2           16DEC2011                  58 2           22AUG2012                 54 2           20FEB2013                  56 2           29MAY2013                 53 What I am looking for is that if the date in Dataset B is within 6 months of the date in Dataset a, then a new variable called "time" will be added, saying 1,2,3,etc. for how many ever match with ** only measurement_a** length (in other words, I do not need to retain values of measurement_b if it does not match the date in Dataset a. Here is an example of what I mean:   Desired result/dataset ID      Time    measure_a    measure_b 1          1           52.3           56 (Dataset B Date = 20JUN2013 - Matched exactly) 1          2           65.6           53 (Dataset B date = 10DEC2013 - Within six months of 12JUL2013 [Dataset A Date]) 1          3           37.4           44 (Dataset B date = 17SEP2014 - Within six months of 28NOV2014 [Dataset A Date]) 1          4           61.3              . (because 17SEP2014 [Dataset B] is closest to 28NOV2014 [Dataset A]) 1          5           40.5           40 (because 23SEP2015 [Dataset B] is closest to 22SEP2015 [Dataset A]) 1          6           60.5              . (No date in Dataset B that is within 6 months of Date in Dataset A [15OCT2015]) 2          1           46.5              . (See below) 2          2           54.1            58 (because 03JUL2011 [Dataset B] is closest to 19JUL2011 [Dataset A]) 2          3           53.6            54 (Dataset B date = 22AUG2012 - Within 6 months of Dataset A date = 29OCT2012)   I have joined on ID but the times is proving difficult. I know it could be the difference in months in the "where" statement in the following code: PROC SQL; CREATE TABLE join_test as SELECT * FROM data_a as a LEFT_JOIN data_b as b ON a.id = b.id WHERE days(a.Date - b.Date) <= 180 ; QUIT; But this does not do the trick. Can some **please** help me? I really appreciate it. Thanks in advance. ... View more