Checking if a column exists or not

TorstenS

Hi!

I have a data source which returns a result set which may or may not include a given column "foo".

Now I would like to create a calculated column with an expression like:

if column foo exists
foo * 2
else
123

Obviously, as soon as I try to code something like

row["foo"]

and there is no column like that, I will get an exception.

Even if(row["foo"] == null) does not do the trick.

Any ideas?

Regards,
Torsten

mwilliams

Hi Torsten,<br />
<br />
I did the following in BIRT 2.5.1.<br />
<br />
In the afterOpen method of your dataSet you can put the following:<br />
<br />
<pre class='_prettyXprint _lang-auto _linenums:0'>
columns = this.getColumnMetaData().getColumnCount();
i=1;
check=0;
while(i <= columns){
if (this.getColumnMetaData().getColumnName(i) == "foo"){
check = 1;
}
i++;
}
</pre>
<br />
Then, in your computed column, to go with your example, you'd put:<br />
<br />
<pre class='_prettyXprint _lang-auto _linenums:0'>
if (check == 1){
row["foo"] * 2;
}
else{
123
}
</pre>
<br />
Not sure if this will work in earlier versions if you're using something earlier than 2.5. Let me know if you have questions or issues.