I have a first table "results" of size 5313 rows and a second table "Lpp_sans_rss" size 3889 rows. I would like to create a merge between the tables by adding only the second column "lpp_libelle" from the second table in the last column of the first table. My problem is : when i make merge between these two tables, i get "124556" rows. I want to keep the same size of the first table by adding the "libell" of each "lpp_code"
Example of table 1 :
953082;IMP RES SEPRAFILM 13X15CM 430103 (A56D)
3115092;ENDOPROT CORONAIRE, STENT LIB. ZOTAROLIMUS, MEDTRONIC,RESOLUTE INTEGRITY,3MM.
The left outer join (or simply left join) described in the following question should solve your problem.
merge(x = results, y = Lpp_sans_rss, by = "ENTERHEREYOURCRITERIA", all.x = TRUE)