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Comparing two tables and copy elements of table 2 into table 1

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Hi,I have two tables as given below.
Table 1:
Table 2
If column1 in table 2 is equal to column 1 in table1 T & W values in table 2 has to copy in table 1, Similar strings has to follow one after the other. If the stings are unequal T & W must be empty. I want the output as below table;
image.PNG
  2 comentarios
dpb
dpb el 14 de Mzo. de 2019
Your new table now has three 'hi' records instead of original two but only two 'hello'.
What's the difference and what's the logic behind such that could be written?
Haritha
Haritha el 15 de Mzo. de 2019
Hi,
I will edit that table

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Respuesta aceptada

Guillaume
Guillaume el 14 de Mzo. de 2019
%create demo tables
ID = strsplit('hello new world hi hello hi')';
T = cell(6, 1); W = T;
V = [1; 2; 3; 5; 8; 7];
T1 = table(ID, T, W, V)
T2 = table(ID(4:5), {2;4}, {6;7}, [1;2], 'VariableNames', {'ID', 'T', 'W', 'V'})
%merge the two tables
[found, where] = ismember(T1.ID, T2.ID);
T1(found, {'T', 'W'}) = T2(where(found), {'T', 'W'})
  3 comentarios
Haritha
Haritha el 20 de Mzo. de 2019
Its working for normal tables. I forget to mention the SQL. I accepted my mistake
Ayse YILMAZ
Ayse YILMAZ el 19 de Abr. de 2021
Hello Guillaume;
Firstly thank you for your helpful sharing. I have a question about your answer.
When I run your code in Matlab, it returns 0 as the value that is not in T2. I wonder if there is a way to return it as space or NAN or something else? What code should I write for this?
Another question is what should I do for more than two tables comparison (7 or 8 tables)?
Thank you in advance for your answer.

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Más respuestas (2)

Pruthvi G
Pruthvi G el 14 de Mzo. de 2019
Use
strcmp
if the values are matching then add the values to the T and W column

Peter Perkins
Peter Perkins el 20 de Mzo. de 2019
This is just an outer join:
>> T1 = table(["hello";"new";"world";"hi";"hello";"hi"],[1;2;3;5;8;7],'VariableNames',["Word" "V"])
T1 =
6×2 table
Word V
_______ _
"hello" 1
"new" 2
"world" 3
"hi" 5
"hello" 8
"hi" 7
>> T2 = table(["hi";"hello"],[2;4],[6;7],'VariableNames',["Word" "T" "W"])
T2 =
2×3 table
Word T W
_______ _ _
"hi" 2 6
"hello" 4 7
>> outerjoin(T1,T2,'MergeKeys',true)
ans =
6×4 table
Word V T W
_______ _ ___ ___
"hello" 1 4 7
"hello" 8 4 7
"hi" 5 2 6
"hi" 7 2 6
"new" 2 NaN NaN
"world" 3 NaN NaN
  1 comentario
Guillaume
Guillaume el 20 de Mzo. de 2019
Editada: Guillaume el 20 de Mzo. de 2019
Do'h! I did try using an outerjoin but using only Word as the key hence got duplicate V, T and W in the result, which I couldn't merge. Of course, If you use all columns as keys, then you get the correct outerjoin.
Note that since the data is stored in a database you don't need matlab to do the join. In SQL it'd be something like:
SELECT * FROM table1 FULL OUTERJOIN table2 ON table.Word = table2.Word

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