Update statement error I don't understand

[Tom]

Normally in that case you would use MERGE statement in a data step.

data fixed;
  merge  original updates;
  by key vars ;
run;

Although you might want to use the orignal UPDATE statement (that has nothing to do with the SQL statement with the same name).  That is designed to apply transactions.  That way you only need to enter the values that change in the transaction dateset since with UPDATE missing values do not replace the original value.  So you only need to enter the values that need to change.