Blank FieldName result

[pjaredchurch]

Hi,

Can anyone help me with result from FieldName() function that is sometimes returning a blank instead of a fieldname?

I have a function that goes through list of columns in a table to remove temporary columns. In my case the temporary columns all have fomat <name>.tmp. Script is below.

The problem that I'm having is two of the columns are getting missed, and when i analyse why, I'm finding that FieldName() function is returning a blank result for them.

Here is the script:

    for i=1 to NoOfFields('$(tableName)')
        vFieldName=FieldName($(i),'$(tableName)');
        trace fieldNumber=$(i),tableName=$(tableName),vFieldName=$(vFieldName);

        if wildmatch('$(vFieldName)','*.tmp') then
            drop field $(vFieldName) from $(tableName);
        end if;
    next;

[Arthur_Fong]

What is the column name that is missing?

[Arthur_Fong · Accepted solution]

Comment the if statement and you will see the difference:

// if wildmatch('$(vFieldName)','*.tmp') then
// drop field $(vFieldName) from $(tableName);

//end if

This is because you cannot drop the columns in the table using for loop.

Once you dropped the columns, the fieldname() function will differs as in original.

Eg:

In the ori table, it has 3 columns [a,b,c].

When the if statement is true, the number  of columns -1 due to drop statement. [b,c]

In the for loop, number of columns still remains as 3, which is incorrect as the number of columns now reduced to 2.

[pjaredchurch]

Thanks Arther,

So I need to do the forloop to get the list of fields that I want to drop, and then drop them as a second step once I'm outside the for loop.

Or perhaps, I could drop the the field inside the for loop, and then decrement the value of $(i) for each field dropped... (I'm guessing it'd probably work based on the behaviour I've seen, but I'm not sure I'd consider it good coding practice).