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

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Haritha
Haritha 2019-3-14
评论： Ayse YILMAZ 2021-4-19
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 个评论
dpb
dpb 2019-3-14
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?

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采纳的回答

Guillaume
Guillaume 2019-3-14
%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'})
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显示 1更早的评论
Haritha
Haritha 2019-3-20
Its working for normal tables. I forget to mention the SQL. I accepted my mistake
Ayse YILMAZ
Ayse YILMAZ 2021-4-19
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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更多回答（2 个）

Pruthvi G
Pruthvi G 2019-3-14
Use
strcmp
if the values are matching then add the values to the T and W column
Peter Perkins
Peter Perkins 2019-3-20
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 个评论
Guillaume
Guillaume 2019-3-20
编辑：Guillaume 2019-3-20
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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