|
Size: 1160
Comment:
|
← Revision 4 as of 2025-10-24 16:34:25 ⇥
Size: 915
Comment: Rewrite
|
| Deletions are marked like this. | Additions are marked like this. |
| Line 13: | Line 13: |
| If the left and right datasets may overlap, use the [[Stata/Merge|merge]] command to ensure that duplicates are not created. | If the left and right datasets may overlap, use [[Stata/Merge|-merge-]] to ensure that duplicates are not created. |
| Line 20: | Line 20: |
| If they are known to not overlap, the [[Stata/Append|append]] command can be used instead. | If they are known to not overlap, consider using [[Stata/Append|-append-]] instead. |
| Line 27: | Line 27: |
| See also the [[Stata/FrLink|frlink]] command. | See also [[Stata/FrLink|-frlink-]]. |
| Line 33: | Line 33: |
| == Left Join == | == Left, Right, or Inner Joins == |
| Line 35: | Line 35: |
| Use the `merge` command as above and select cases based on the created `_merge` variable. | Use [[Stata/Merge|-merge-]] as above and select cases based on the automatically created `_merge` variable. |
| Line 40: | Line 40: |
| keep if _merge==1 | _merge==3 | keep if _merge==1 | _merge==3 // left join keep if _merge==2 | _merge==3 // right join keep if _merge==3 // inner join |
| Line 42: | Line 44: |
Alternatively, try using the '''`keep(groups)`''' option. {{{ use "left.dta" merge 1:1 KEYVARS using "right.dta", keep(1 3) }}} See also the [[Stata/FrLink|frlink]] command. ---- == Right Join == As with the left join, but the groups of interest are 2 and 3. ---- == Inner Join == As with the left join, but only group 3 is of interest. |
Joining Data with Stata
Stata offers several commands for joining datasets.
Full Join
If the left and right datasets may overlap, use -merge- to ensure that duplicates are not created.
use "left.dta" merge 1:1 KEYVARS using "right.dta"
If they are known to not overlap, consider using -append- instead.
use "cohort1.dta" append using "cohort2.dta"
See also -frlink-.
Left, Right, or Inner Joins
Use -merge- as above and select cases based on the automatically created _merge variable.
use "left.dta" merge 1:1 KEYVARS using "right.dta" keep if _merge==1 | _merge==3 // left join keep if _merge==2 | _merge==3 // right join keep if _merge==3 // inner join