/*********************************************************************

FILENAME: TOTALUPDATE.SAS
SUBJECT HEADING:  DATA
INITIALS:  BML
DATE:  31 JUL 96
PROGRAM:  SAS
VERSION:  6.11 TS040
PLATFORM:  WINDOWS
TITLE:  UNCONDITIONALLY REPLACE THE VALUES OF A DATASET WITH NEW VALUES
        FROM A TRANSACTION DATASET

DESCRIPTION:  IF YOU WANT TO UNCONDITIONALLY REPLACE THE VALUES IN ONE
DATASET WITH VALUES FROM ANOTHER DATASET, THIS CODE WILL DO IT.  THERE
MUST BE AN ID VARIABLE IN BOTH DATASETS THAT UNIQUELY IDENTIFIES EACH
CASE.

**********************************************************************/

options linesize=72;

/*

FIRST WE CREATE A MASTER DATASET THAT CONTAINS MISSING VALUES FOR SOME OF
THE VARIABLES. 

*/

data master;

  input id var1 var2 $ var3;
  datalines;
  1 3478 able    234.45
  2 4562 .       634.23
  3 .    charlie .
  4 5695 delta   . 
  5 .    .       575.12
  ;

proc print data=master;
  title 'printout of master dataset with missing values';
run;

/*

NOW WE CREATE A TRANSACTION DATASET THAT HAS REPLACEMENT VALUES FOR SOME 
OF THE MISSING DATA IN THE MASTER DATASET.

*/

data transact;

  input id var1 var2 $ var3;
  datalines;
  3 . .     999.99
  5 . gamma 999.99
  ;

proc print data=transact;
  title 'printout of transaction dataset with replacement values';
run;

/* 

NOW WE SORT BOTH DATA SETS BY THE COMMON CASE ID VARIABLE.

*/

proc sort data=master;
  by id;
proc sort data=transact;
  by id;
run;

/*

FINALLY, WE UPDATE THE MASTER DATASET WITH THE NEW VALUES.  NOTE THAT THE 
TRANSACTION DATASET COMES SECOND IN THE UPDATE STATEMENT.  ALSO NOTE THAT
EVERY ORIGINAL VALUE HAS BEEN REPLACED WITH A NEW VALUE.  IN SOME CASES,
VALID DATA HAS BEEN REPLACED WITH A MISSING VALUE!

*/

data final(drop=newvar1 newvar2 newvar3);

  present = 0;

  merge master(in=present)
        transact(rename=(var1=newvar1 var2=newvar2 var3=newvar3));

  by id;

  var1 = newvar1;
  var2 = newvar2;
  var3 = newvar3;

  if present;

run;

proc print data=final;

  title 'printout of dataset with updated values';

run;