Dear
My dataset is split across two large files. the master file has 10,000 respondents all uniquely identified with a unique id. However, in the second file has only 9800 respondents as 200 decided not to participate. I need to merge some variables from the second file into the master file but I am not able to do it as the number of observation don't match across the two files. I have tried using 1:1 merge function but this given an error.
variable unique_identifier does not uniquely identify observations in the using data
r(459);

Can anyone help please?