Error merging files: . Error says that variable CLAIM_NUMBER does not uniquely identify observations in the using data. How do I fix that?

Question

In Stata, the error says that variable CLAIM_NUMBER does not uniquely identify observations in the using data. How do I fix that? My code:

cd"abcd"
use NY2019_2021
merge m:1 CLAIM_NUMBER using FULLNY
keep if _merge==3
drop _merge```

Answer 1

I was able to drop the ones that weren't unique code:

duplicates list CLAIM_NUMBER
duplicates drop CLAIM_NUMBER, force