Update row in database
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Hi ..
In database I have Id and its type is 'int', also I have Name and its type is varchar
When I tried to update the Id it was work:
Id = str2num(get(handles.ID,'String'));
y = exec(conn,'select Id from admin_info')
y = fetch(y);
y1=(y.Data)
colnames3={'Id'};
whereclause3 = ['WHERE ID= ' num2str(y1{1})]
update(conn,'admin_info', colnames3, Id, whereclause3);
But the update for the name it doesn't work !
name = get(handles.name, 'String')
x = exec(conn,'select name from admin_info');
x = fetch(x);
x1 = x.Data
n = x1{1}
colnames2={'name'};
whereclause2 = ['WHERE name = ' n]
update(conn,'admin_info', colnames2, name, whereclause2);
7 个评论
Han
2018-3-21
Bob Thompson
2018-3-21
Is it giving you a specific error? If so would you please post it along with which line is causing the error.
Also, what type of variable is 'n'?
Han
2018-3-21
Bob Thompson
2018-3-21
Ok, if there is not error how do you know that it is wrong? What results is it giving you, and what would you expect?
Han
2018-3-21
Bob Thompson
2018-3-21
I realize this is things you probably already checked, but it's what I usually go through to investigate my errors.
Have you confirmed that name, n, and whereclause2 are all proper values and classes?
If those are all correct, then it appears that all of the inputs to the update() command are correct and I don't know that I'm really going to be able to help you much, since I don't really know anything about Simulink commands.
I may be way off here (not a lot of experience with databases), but:
It looks like you are retrieving the entire column from the database, using MATLAB to find the row you want to change, then telling the database to change it. Why not build a single exec command and let the database do it all?
Otherwise, I notice you have a space before the = in the second where clause, but not the first. I don't think that matters, but maybe?
采纳的回答
Greg
2018-3-22
Reading the documentation for update, it indicates that the new data (input number 4) cannot be a character array. The ID worked because it can handle numeric matrix. To update a char/string entry, use a cellstr input.
update(conn,'admin_info', colnames2, cellstr(name), whereclause2);
6 个评论
Han
2018-3-22
Bob Thompson
2018-3-22
I had no problems producing a character string for whereclause using two different methods:
whereclause2 = ['WHERE name = ' n]; % Your method
whereclause2 = strcat('WHERE name = n ',n); % Additional method
You may be running into the same issue as what Greg mentioned with the string vs character issue, so maybe use cellstr() to convert the character array into a string.
Han
2018-3-22
Han
2018-3-22
Bob Thompson
2018-3-22
编辑：Bob Thompson
2018-3-22
You don't want to do cellstr(n), you want cellstr(whereclause2).
Of course I could also be totally just blowing smoke and have no idea what I'm doing.
Han
2018-3-22
更多回答（1 个）
Han
2018-3-22
1 个评论
That is extremely complex code.
x = exec(conn,'select name from admin_info');
x = fetch(x);
colnames2={'name'};
% Probably want an actual index here, not a hardcoded 1
whereclause2 = sprint('WHERE name = ''%s''',x.Data{1});
Your use of
xx = char(x.Data);
will not do well when x.Data has multiple rows.
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