Merging two data with two common variables and appending it to previous merged data

[Beatrice Lee]

I am trying to merge two data and appending it to the previous merged data.

Below are my Stata codes

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clear all
set more off, permanently
use "U:\state\ARUNACHAL PRADESH.dta" (A state file with lots of districts)

levelsof distname, local(dis) (Trying to extract the district names)
>"CHANGLANG"' `"DIBANG VALLEY"' `"EAST KAMENG"' `"EAST SIANG"' `"KURUNG KUMEY"' `"LOHIT"' `"LOWER DIBANG VALLEY"' `
> "LOWER SUBANSIRI"' `"PAPUM PARE"' `"TAWANG"' `"TIRAP"' `"UPPER SIANG"' `"UPPER SUBANSIRI"' `"WEST KAMENG"' `"WEST
> SIANG"'

foreach s of local dis {
use "U:\Excel file\Arunachal Pradesh _`s'.dta"

merge 1:1 distname blkname using "U:\state\ARUNACHAL PRADESH.dta"
tostring BlockDifference, replace

append using "U:\merge\Arunachal Pradesh.dta"
save "U:\merge\Arunachal Pradesh.dta", replace
}

>(note: variable distname was str9, now str25 to accommodate using data's values)
>(note: variable blkname was str14, now str35 to accommodate using data's values)

>variables distname blkname do not uniquely identify observations in the using data
r(459);


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Then the error message pops out and when I browse the data,
there is only the first district (CHANGLANG)'s data.

What could have I done wrong?

[Evelyn Ersanilli]

The error message suggests that your file "U:\state\ARUNACHAL PRADESH.dta" contains more than one observation with the same values on "distname blkname".
Did you check this?

An easy way of doing this is creating a variable that helps you identity combinations of distname blkname that occur more than once

bys distname blkname : gen count=_n

list distname blkname if count>1

[Beatrice Lee]

There are bunch of same distnames but different blknames, and also other cases with same blknames but different distnames. So I wanted to actually merge them with same distname&blknames.. But I am not sure how...

[Svend Juul]

Obviously you have duplicates with the same distname&blkname. Would it be valid to do a 1:m merge? What is "them" in:

So I wanted to actually merge them with same distname&blknames.