Using Sql in matlab to get data

Hello!

I hope you're doing well.

I want to get specific rows from my data base that have specific IDs.

ID = [8 , 4, 3];
ID = num2str(MissingTrips);
DD = ['SELECT * ' 'FROM Countries WHERE IDNr =',ID]; DD = fetch(conn,DD );

but matlab thinks I'm trying to horzcat when I'm trying to get the data with these IDs, I tried to do mat2str instead of num2str but nothing. How can I get my rows from my Countries table? while usind ID, all at once?

I would appreciat your help on how I can proceed.

Thank you!

Answer 1

[Guillaume]

Two things about what you've written, a matlab one, and a sql one,

Matlab:

DD = ['SELECT * ' 'FROM Countries WHERE IDNr =']

is the same thing as

DD = ['SELECT * ', 'FROM Countries WHERE IDNr =']

It is a concatenation indeed and I recommend that you always put the , separator so the reader don't have to wonder if you made a mistake. Of course the result of that is:

DD ='SELECT * FROM Countries WHERE IDNr ='

so it's not clear why you didn't write that to start with.

SQL:

WHERE x = y

only allows you to specify one value for y, no more. So your SQL syntax is not correct. To select among a list of values, you use

WHERE x IN (val1, val2, val3, ..)

One way you could compose your statement:

ID = [8 , 4, 3];
IDstring = strjoin(compose('%d', ID), ',');
SQL = sprintf('SELECT * FROM Countries WHERE IDNr IN (%s)', IDstring);

[John Doe]

Thank you!