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Hi I'm trying to combine 2 datasets with a common key which I'm not able to resolve with JoinAcross. 1st dataset is

names = Dataset[{
            <|"UID" -> "UID1", "FN" -> "FirstName1", "LN" -> "LastName1"|>,
            <|"UID" -> "UID2", "FN" -> "FirstName2", "LN" -> "LastName2"|>,
            <|"UID" -> "UID3", "FN" -> "FirstName3", "LN" -> "LastName3"|>,
            <|"UID" -> "UID4", "FN" -> "FirstName4", "LN" -> "LastName4"|>,
            <|"UID" -> "UID5", "FN" -> "FirstName5", "LN" -> "LastName5"|>}];

and the second dataset is 

records = Dataset[{<|"UID1" -> "record1"|>, 
                    <|"UID1" -> "record2"|>, 
                    <|"UID1" -> "record3"|>,
                    <|"UID3" -> "record4"|>,
                    <|"UID3" -> "record5"|> ,
                    <|"UID3" -> "record6"|> ,
                    <|"UID5" -> "record7"|> }];

I'm trying to get a combined dataset which would look like this:

wanted = Dataset[{
    <|"FN" -> "FirstName1", "LN" -> "LastName1", "UID1" -> "record1"|>, 
    <|"FN" -> "FirstName1", "LN" -> "LastName1", "UID1" -> "record2"|>, 
    <|"FN" -> "FirstName1", "LN" -> "LastName1", "UID1" -> "record3"|>,
    <|"FN" -> "FirstName3", "LN" -> "LastName3", "UID3" -> "record4"|>,
    <|"FN" -> "FirstName3", "LN" -> "LastName3", "UID3" -> "record5"|> ,
    <|"FN" -> "FirstName3", "LN" -> "LastName3", "UID3" -> "record6"|> ,
    <|"FN" -> "FirstName5", "LN" -> "LastName5", "UID5" -> "record7"|> }];

In other words, I'm trying to get names from userID in first data set tied to full name and records in 2nd dataset.

JoinAcross is of no help. Any help is appreciated.

Thanks, Gani -

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This is how I would do it

names = {<|"UID" -> "UID1", "FN" -> "FirstName1", 
    "LN" -> "LastName1"|>, <|"UID" -> "UID2", "FN" -> "FirstName2", 
    "LN" -> "LastName2"|>, <|"UID" -> "UID3", "FN" -> "FirstName3", 
    "LN" -> "LastName3"|>, <|"UID" -> "UID4", "FN" -> "FirstName4", 
    "LN" -> "LastName4"|>, <|"UID" -> "UID5", "FN" -> "FirstName5", 
    "LN" -> "LastName5"|>};

records = {<|"UID1" -> "record1"|>, <|"UID1" -> "record2"|>, <|
    "UID1" -> "record3"|>, <|"UID3" -> "record4"|>, <|
    "UID3" -> "record5"|>, <|"UID3" -> "record6"|>, <|
    "UID5" -> "record7"|>};

names = Association[#UID -> # & /@ names]

records = First@Normal@# & /@ records

f2[x0_] := 
 With[{uid = x0[[1]]}, <|"FN" -> names[uid]["FN"], 
   "LN" -> names[uid]["LN"], uid -> x0[[2]]|>]

wanted = f2 /@ records

Skip the wrapping of Dataset, it will not help with your non-normalized datastructure, and it general, wrapping with Dataset is only helpful for display of final output

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  • $\begingroup$ thanks for the elegant solution. Now, I need to step through it to digest what you've done! gani- $\endgroup$
    – Gani Ganapathi
    Dec 12 '19 at 4:20
  • 1
    $\begingroup$ Using Composition. records = First@*Normal /@ records. $\endgroup$
    – Rohit Namjoshi
    Dec 12 '19 at 15:01
  • $\begingroup$ @GaniGanapathi Please don't hesitate to ask for help! All the best $\endgroup$
    – Manuel --Moe-- G
    Dec 12 '19 at 19:05

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