Hi Stata Users,

I am new to this forum (but not new to Stata). I am having a problem with merging two data sets (many duplicates in zipcode variable the two datasets). I haven't faced this issue before and I would like to have some help, please.

The first dataset is: staion_info_A

Code:
* Example generated by -dataex-. To install: ssc install dataex
clear
input long zipcode str11 stationcode str18 AreaType str16 station_latitude str17 station_longitude
91522 "DEBY001" "urban"           "49.30489"  "10.572297"
95659 "DEBY002" "suburban"        "50.058193" "12.18865"
63739 "DEBY003" "urban"           "49.971478" "9.1508"   
63839 "DEBY004" "rural_near_city" "49.869419" "9.171545"
63741 "DEBY005" "suburban"        "49.991516" "9.117972"
86150 "DEBY006" "urban"           "48.36459"  "10.895028"
86153 "DEBY007" "urban"           "48.376575" "10.88837"
86179 "DEBY008" "suburban"        "48.30827"  "10.907772"
96047 "DEBY009" "urban"           "49.898331" "10.887686"
95444 "DEBY010" "urban"           "49.947083" "11.575755"
94249 "DEBY011" "rural_remote"    "49.109901" "13.107995"
84489 "DEBY012" "suburban"        "48.177174" "12.829314"
84561 "DEBY013" "rural_regional"  "48.182835" "12.781385"
96450 "DEBY014" "urban"           "50.260578" "10.959311"
91052 "DEBY015" "urban"           "49.596649" "11.017347"
91052 "DEBY016" "suburban"        "49.587601" "11.016617"
91056 "DEBY017" "rural_near_city" "49.589985" "10.933278"
91058 "DEBY018" "suburban"        "49.551762" "11.031158"
94089 "DEBY019" "rural_remote"    "48.780891" "13.80355"
95030 "DEBY020" "suburban"        "50.32061"  "11.897491"
85049 "DEBY021" "urban"           "48.769192" "11.428767"
85119 "DEBY022" "rural_near_city" "48.727795" "11.577191"
85080 "DEBY023" "suburban"        "48.780815" "11.372636"
85055 "DEBY024" "suburban"        "48.787811" "11.445275"
85098 "DEBY025" "rural_near_city" "48.766415" "11.524258"
85088 "DEBY026" "suburban"        "48.769028" "11.616809"
63796 "DEBY027" "urban"           "50.068741" "9.006667"
93309 "DEBY028" "urban"           "48.909519" "11.879245"
93309 "DEBY029" "suburban"        "48.924603" "11.874416"
93342 "DEBY030" "suburban"        "48.904228" "11.948794"
87439 "DEBY031" "suburban"        "47.72514"  "10.306561"
95326 "DEBY032" "urban"           "50.103134" "11.442592"
84028 "DEBY033" "urban"           "48.539799" "12.157049"
91207 "DEBY034" "suburban"        "49.506504" "11.273913"
88131 "DEBY035" "urban"           "47.55439"  "9.690022"
95192 "DEBY036" "rural_near_city" "50.382484" "11.675161"
80335 "DEBY037" "urban"           "48.137253" "11.564925"
81679 "DEBY038" "urban"           "48.152359" "11.613809"
80335 "DEBY039" "urban"           "48.154533" "11.554669"
81241 "DEBY040" "urban"           "48.146351" "11.465603"
81541 "DEBY041" "urban"           "48.125278" "11.582152"
81547 "DEBY042" "urban"           "48.107296" "11.5823"  
80992 "DEBY043" "urban"           "48.179024" "11.514714"
80804 "DEBY044" "urban"           "48.1702"   "11.568341"
80686 "DEBY045" "urban"           "48.131565" "11.519369"
81379 "DEBY046" "urban"           "48.098095" "11.528664"
95119 "DEBY047" "rural_near_city" "50.323246" "11.721605"
93326 "DEBY048" "suburban"        "48.813324" "11.860506"
93333 "DEBY049" "rural_regional"  "48.85321"  "11.777817"
93333 "DEBY050" "rural_near_city" "48.764273" "11.75372"
93333 "DEBY051" "rural_near_city" "48.773136" "11.69925"
89231 "DEBY052" "urban"           "48.397079" "10.008291"
90478 "DEBY053" "urban"           "49.445911" "11.088444"
90411 "DEBY054" "urban"           "49.477066" "11.105847"
90441 "DEBY055" "urban"           "49.434734" "11.049103"
90762 "DEBY056" "urban"           "49.472214" "10.984706"
90482 "DEBY057" "urban"           "49.46273"  "11.143267"
90429 "DEBY058" "urban"           "49.462227" "11.025472"
90471 "DEBY059" "urban"           "49.430645" "11.103631"
90403 "DEBY060" "urban"           "49.453209" "11.074473"
94032 "DEBY061" "urban"           "48.572224" "13.456372"
94209 "DEBY062" "suburban"        "48.972401" "13.128934"
93047 "DEBY063" "urban"           "49.019016" "12.101856"
93057 "DEBY064" "urban"           "49.033585" "12.124537"
83022 "DEBY065" "urban"           "47.85617"  "12.118842"
91126 "DEBY066" "urban"           "49.323704" "11.071397"
92421 "DEBY067" "suburban"        "49.321957" "12.128139"
97421 "DEBY068" "urban"           "50.048397" "10.232075"
95100 "DEBY069" "suburban"        "50.176365" "12.128364"
92237 "DEBY070" "urban"           "49.501595" "11.750048"
92237 "DEBY071" "urban"           "49.501595" "11.750048"
93464 "DEBY072" "rural_regional"  "49.438465" "12.54887"
95643 "DEBY073" "suburban"        "49.879005" "12.332447"
95485 "DEBY074" "rural_regional"  "49.987204" "11.80332"
92637 "DEBY075" "urban"           "49.678951" "12.159361"
97070 "DEBY076" "urban"           "49.794579" "9.935939"
97080 "DEBY077" "suburban"        "49.804695" "9.956419"
97072 "DEBY078" "urban"           "49.773281" "9.93775"  
83435 "DEBY079" "urban"           "47.723186" "12.858856"
83435 "DEBY080" "rural_remote"    "47.701761" "12.879267"
82467 "DEBY081" "rural_near_city" "47.476395" "11.063066"
82467 "DEBY082" "rural_remote"    "47.508499" "11.142889"
82467 "DEBY083" "rural_remote"    "47.421227" "10.985722"
87534 "DEBY084" "rural_remote"    "47.497712" "10.074031"
81377 "DEBY085" "urban"           "48.113098" "11.517227"
85445 "DEBY086" "rural_near_city" "48.354026" "11.822676"
85354 "DEBY087" "rural_near_city" "48.344657" "11.708521"
83308 "DEBY088" "suburban"        "48.02166"  "12.538176"
81929 "DEBY089" "suburban"        "48.173195" "11.648036"
83080 "DEBY090" "rural_near_city" "47.647442" "12.173597"
84375 "DEBY091" "rural_near_city" "48.231201" "12.971764"
82362 "DEBY092" "suburban"        "47.84687"  "11.16085"
92237 "DEBY093" "suburban"        "49.487984" "11.786342"
86179 "DEBY099" "suburban"        "48.326012" "10.903049"
82346 "DEBY109" "rural_regional"  "47.968754" "11.220172"
86150 "DEBY110" "urban"           "48.370373" "10.896822"
95444 "DEBY111" "urban"           "49.943638" "11.570088"
85399 "DEBY112" "rural"           "48.339193" "11.736532"
91056 "DEBY113" "suburban"        "49.605911" "10.963528"
80538 "DEBY114" "urban"           "48.142742" "11.59228"
end
the secon data set is: staion_info_B

Code:
* Example generated by -dataex-. To install: ssc install dataex
clear
input long zipcode double areakm2 str35(county city) float population
91183  48.41 "Roth"                        "Abenberg"                    5.511
93326  60.26 "Kelheim"                     "Abensberg"                  13.946
91720  18.98 "Weissenburg-Gunzenhausen"    "Absberg"                     1.361
97355  12.81 "Kitzingen"                   "Abtswind"                      862
94250  30.04 "Regen"                       "Achslach"                      921
85111  51.95 "Eichstatt"                   "Adelschlag"                  3.006
91325  31.68 "Erlangen-Hochstadt"          "Adelsdorf"                   8.366
91587  27.18 "Ansbach"                     "Adelshofen"                    955
82276  13.28 "Furstenfeldbruck"            "Adelshofen"                  1.713
86477    9.7 "Augsburg"                    "Adelsried"                   2.357
86559  16.95 "Aichach-Friedberg"           "Adelzhausen"                 1.705
84166  47.86 "Landshut"                    "Adlkofen"                    4.321
86444  44.82 "Aichach-Friedberg"           "Affing"                      5.476
84168  38.01 "Landshut"                    "Aham"                        1.912
94345   21.4 "Straubing-Bogen"             "Aholfing"                    1.828
94527  29.35 "Deggendorf"                  "Aholming"                    2.238
96482  19.83 "Coburg"                      "Ahorn"                       4.244
95491  43.47 "Bayreuth"                    "Ahorntal"                    2.162
94529  20.35 "Passau"                      "Aicha vorm Wald"             2.401
86551  92.83 "Aichach-Friedberg"           "Aichach"                    21.434
86479  17.62 "Gunzburg"                    "Aichen"                      1.154
94501   17.1 "Passau"                      "Aidenbach"                   2.948
97491   37.3 "Hassberge"                   "Aidhausen"                   1.689
84089  39.85 "Kelheim"                     "Aiglsbach"                   1.768
86447  31.38 "Aichach-Friedberg"           "Aindling"                    4.458
83404  32.96 "Berchtesgadener Land"        "Ainring"                     9.908
89344  19.35 "Dillingen an der Donau"      "Aislingen"                   1.299
94330  43.09 "Straubing-Bogen"             "Aiterhofen"                  3.339
87648  30.73 "Ostallgau"                   "Aitrang"                     2.037
83544  18.16 "Rosenheim"                   "Albaching"                   1.757
97320    3.8 "Kitzingen"                   "Albertshofen"                2.315
94501   45.8 "Passau"                      "Aldersbach"                  4.273
86733  23.37 "Donau-Ries"                  "Alerheim"                    1.637
91793  20.45 "Weissenburg-Gunzenhausen"    "Alesheim"                      953
86480  17.65 "Gunzburg"                    "Aletshausen"                 1.172
91236  17.95 "Nurnberger Land"             "Alfeld"                      1.076
90584   59.7 "Roth"                        "Allersberg"                  8.337
85391  26.55 "Freising"                    "Allershausen"                5.847
82239  21.02 "Furstenfeldbruck"            "Alling"                      3.903
86695  10.32 "Augsburg"                    "Allmannshofen"                 902
84032  22.99 "Landshut"                    "Altdorf"                    11.215
90518  48.59 "Nurnberger Land"             "Altdorf bei Nurnberg"       15.245
93087  13.22 "Regensburg"                  "Alteglofsheim"               3.316
97901  37.64 "Miltenberg"                  "Altenbuch"                   1.225
96146    8.7 "Bamberg"                     "Altendorf"                    2.12
92540  23.17 "Schwandorf"                  "Altendorf"                     855
96264   32.9 "Lichtenfels"                 "Altenkunstadt"               5.383
83352   26.1 "Traunstein"                  "Altenmarkt an der Alz"       4.181
86450  41.15 "Augsburg"                    "Altenmunster"                4.107
89281   31.3 "Neu-Ulm"                     "Altenstadt"                  5.109
86972  18.66 "Weilheim-Schongau"           "Altenstadt"                  3.319
92665  22.06 "Neustadt an der Waldnaab"    "Altenstadt an der Waldnaab"  4.793
93177  21.48 "Regensburg"                  "Altenthann"                   1.48
97237  24.06 "Wurzburg"                    "Altertheim"                  2.006
84169  24.29 "Landshut"                    "Altfraunhofen"               2.393
82278  16.09 "Furstenfeldbruck"            "Althegnenberg"               2.024
93336 114.13 "Eichstatt"                   "Altmannstein"                7.001
85250  75.66 "Dachau"                      "Altomunster"                 7.925
87452  91.68 "Oberallgau"                  "Altusried"                  10.086
84503  23.07 "Altotting"                   "Altotting"                  12.969
63755   59.3 "Aschaffenburg"               "Alzenau"                    18.469
92224  50.13 "kreisfreie Stadt"            "Amberg"                      41.97
86854  10.96 "Unterallgau"                 "Amberg"                      1.476
83123  39.81 "Rosenheim"                   "Amerang"                     3.659
86735  19.11 "Donau-Ries"                  "Amerdingen"                    841
90614   5.06 "Furth"                       "Ammerndorf"                  2.058
92260   8.14 "Amberg-Sulzbach"             "Ammerthal"                   2.091
63916   50.9 "Miltenberg"                  "Amorbach"                     3.99
84539  31.13 "Muhldorf am Inn"             "Ampfing"                     6.576
82346  40.43 "Starnberg"                   "Andechs"                     3.751
83454  45.91 "Berchtesgadener Land"        "Anger"                       4.542
91522  99.91 "kreisfreie Stadt"            "Ansbach"                    41.847
82387  22.38 "Weilheim-Schongau"           "Antdorf"                      1.34
85646  16.18 "Ebersberg"                   "Anzing"                      4.429
86974  12.31 "Landsberg am Lech"           "Apfeldorf"                   1.139
87742  15.01 "Unterallgau"                 "Apfeltrach"                    935
91722  31.29 "Ansbach"                     "Arberg"                      2.264
86561   29.9 "Neuburg-Schrobenhausen"      "Aresing"                     2.855
93471  37.87 "Regen"                       "Arnbruck"                     1.94
93473  28.32 "Cham"                        "Arnschwang"                  2.009
97450  112.1 "Main-Spessart"               "Arnstein"                    8.125
94424  80.37 "Rottal-Inn"                  "Arnstorf"                    6.978
93474  28.81 "Cham"                        "Arrach"                      2.464
95659  43.19 "Wunsiedel im Fichtelgebirge" "Arzberg"                     5.152
86663   11.9 "Donau-Ries"                  "Asbach-Baumenheim"           4.691
94347  19.56 "Straubing-Bogen"             "Ascha"                       1.619
63739  62.45 "kreisfreie Stadt"            "Aschaffenburg"              70.527
63741  62.45 "kreisfreie Stadt"            "Aschaffenburg"              70.527
63743  62.45 "kreisfreie Stadt"            "Aschaffenburg"              70.527
84544  20.76 "Muhldorf am Inn"             "Aschau am Inn"               3.384
83229  79.59 "Rosenheim"                   "Aschau im Chiemgau"          5.731
85609  28.05 "Munchen"                     "Aschheim"                    9.198
84091  31.42 "Kelheim"                     "Attenhofen"                  1.376
85395   16.1 "Freising"                    "Attenkirchen"                2.761
94348  14.92 "Straubing-Bogen"             "Atting"                      1.693
84072  54.99 "Freising"                    "Au in der Hallertau"         6.063
97239  17.54 "Wurzburg"                    "Aub"                         1.466
97633  11.92 "Rhon-Grabfeld a.d.S."        "Aubstadt"                      709
94530  24.07 "Deggendorf"                  "Auerbach"                    2.106
91275  78.25 "Amberg-Sulzbach"             "Auerbach in der Oberpfalz"   8.818
end

I am using these code below; non of them works:

Code:
cd "/Users/Amir/Desktop/Speed_Limit/Recycle"
use staion_info_A, clear

merge 1:1 zipcode using staion_info_B


cd "/Users/Amir/Desktop/Speed_Limit/Recycle"
use staion_info_A, clear

merge 1:m zipcode using staion_info_B

cd "/Users/Amir/Desktop/Speed_Limit/Recycle"
use staion_info_A, clear

merge m:1 zipcode using staion_info_B
Thank you for your help, in advance

Ami