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

Question

Haritha 2019-3-14

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/450053-comparing-two-tables-and-copy-elements-of-table-2-into-table-1

评论： Ayse YILMAZ 2021-4-19

采纳的回答： Guillaume

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;

2 个评论
显示无隐藏无

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?

Haritha 2019-3-15

Hi,

I will edit that table

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Guillaume 2019-3-14

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/450053-comparing-two-tables-and-copy-elements-of-table-2-into-table-1#answer_365368

在 MATLAB Online 中打开

%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 个评论
显示 1更早的评论隐藏 1更早的评论

Haritha 2019-3-20

Its working for normal tables. I forget to mention the SQL. I accepted my mistake

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.

请先登录，再进行评论。

Answer 2

Pruthvi G 2019-3-14

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/450053-comparing-two-tables-and-copy-elements-of-table-2-into-table-1#answer_365365

在 MATLAB Online 中打开

Use

strcmp

if the values are matching then add the values to the T and W column

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

Guillaume 2019-3-14

ismember which uses strcmp would be a lot more useful for this.

请先登录，再进行评论。

Answer 3

Peter Perkins 2019-3-20

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/450053-comparing-two-tables-and-copy-elements-of-table-2-into-table-1#answer_366398

在 MATLAB Online 中打开

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
显示 -1更早的评论隐藏 -1更早的评论

Guillaume 2019-3-20

编辑：Guillaume 2019-3-20

在 MATLAB Online 中打开

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

请先登录，再进行评论。