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Re: st: RE: creating 2 datasets in memory without saving and merge

From   Austin Nichols <>
Subject   Re: st: RE: creating 2 datasets in memory without saving and merge
Date   Fri, 27 Apr 2012 13:32:46 -0400

Nick Cox <>:

One can work with two datasets in memory at once, if the variable
names do not overlap (c.f. the unmatched merge trick described at e.g. It is
only tautologically true that the merged data is one (new) dataset in
memory; in practice both datasets are in memory, though one probably
has extra missing values.

One can also keep two datasets (or more) in Mata matrices.

However, it seems the OP needs to simply -merge- and then save under a
new name. I agree completely on your points 2-4.

On Fri, Apr 27, 2012 at 1:15 PM, Nick Cox <> wrote:
> 1. You can hold precisely one (1) dataset in memory in Stata at once. This is circular in so far as what you hold in memory is always regarded as one (1) dataset, regardless of whether that dataset was originally two or more datasets in some sense, Stata or not Stata. Nevertheless the circularity is not vicious.
> 2. There are various ways of combining two or more datasets, including the use of -merge- or -append- and just typing or pasting in new data into the Editor.
> 3. Whether a dataset has been -save-d is a different question. No rule says that you must -save- data. It would be a waste of effort to combine datasets and not -save- the results if you intend to -use- that dataset later, but that's a practicality, not a rule.
> 4. Why you say that whatever you have in mind is "not good" is completely unclear to me.
> Nick
> tashi lama
>       I will be using 2 diff databases to get my data in stata. And I need to merge those two data to use for my analysis. One obvious way is to get the data from  database 1 and save it with .dta file. Then use another database to pull data in stata memory(this is doable since my memory is clear) and use merge command. Unfortunately, this method is not good since i will have to save one dataset. Is there anyway I could pull two datasets in the memory without saving anyof the datasets? Or, what are my choices to get my intended result. Please let me know if my question is not clear.

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