Date:         Thu, 30 Mar 2000 10:04:54 -0800
Reply-To:     Ya Huang <ya.huang@AGOURON.COM>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         Ya Huang <ya.huang@AGOURON.COM>
Subject:      Merge, why I can't turn off the default retain?
Content-Type: text/plain; charset=us-ascii

Hello all,

It seems that whenever I think I have known something well in SAS,
I'll be proved wrong. This time is "Merge":

data xx;
do x=1 to 2;
do y=1 to 5;
output;
end;
end;

data xx_h (rename=(y=ny));
  set xx;
by x;
if first.x then delete;
else output;

data xx;
  merge xx(in=a) xx_h(in=b);
by x;
if a and not b then ny=.;  /**********/

options nocenter;
proc print;
run;

====================
OBS    X    Y    NY

  1    1    1     2
  2    1    2     3
  3    1    3     4
  4    1    4     5
  5    1    5     5  <== retained
  6    2    1     2
  7    2    2     3
  8    2    3     4
  9    2    4     5
 10    2    5     5  <== retained

Question is why I still get ny retained in obs=5,10?
I expected after using the "if a and not b then ny=." statement,
ny would be missing in obs=5,6. But as you can see,
they are still retained. Can somebody tell me why?

Thanks,

Ya Huang