The LA Fox Developer Newsletter

September 1998

FoxPro Q&A (Con’t from page 7)

How do / troubleshoot the error message ‘illegal Seek Offset’?

This error means that FoxPro is trying to position a File Pointer

beyond the end of the file or before the beginning of the file.

This usually occurs in large databases, when you use the

SEEK command to find a particular record. The most common

reason for this error is that the Index files are corrupted.

To resolve this problem:

Delete all the index tags using the DELETE TAG ALL and

create the Index file again. Don’t use the REIN DEX command

because this does not recreate the Index file header that may

also be corrupted.

In Visual FoxPro, when you issue DELETE TAG ALL on a table

that belongs to a DBC, all the relations this table was involved in

will be deleted. So you will have to set them back programmati-

cally. To add relations programmatically use the ALTER TABLE

command with the ADD and REFERENCES clauses.

How can I group Child Records from two different tables in a

Report?

Suppose you have a parent table, say CUSTOMER that has two

or more child tables, say INVOICES and CONTACTS and you

want to create a report from the tables given below.

CUSTOMER ABC Company 123 Main St. (Parent record)

CONTACTS John Doe (Child record) Jane Doe

INVOICES (Child record) 12345 Widgets, 67890 Things

Here’s what you can do:

‘First, create a dummy table with two memo fields:

CREATE dummy (childi m, child2 m)

APPEND BLANK

‘Now, do a SELECT from the parent table, joining the two memo

fields:

SELECT * FROM parent,dummy INTO TABLE rpttbl

‘Now you have a table just like the parent table, but with two

memo fields to hold related info from the children

INDEX ON keyfield TAG keyfield

‘Here we create a CDX for the rpttbl

SELECT childi SET ORDER TO TAG keyfield

SET RELATION TO keyfield INTO rpttbl ADDITIVE

SCAN

(Con’t, page 4)

is so fast, why don’t we throw some more data at it? Something

along the lines of 200,000 users and 7 million or so demo-

graphic answers.

Frankly I think they were growing tired of my snide remarks

about FoxPro’s abilities and wanted to bring Fox to it’s knees.

They were greatly disappointed when the processing on 7

million records only took 10 seconds.

In the end the client gets an application that runs 2000%

percent faster on 20 times as much data. Another happy

customer. Another successful FoxPro application.

Join

LA Fox

It Can’t Get Any Easier.......

We’ve come up with an easy way to submit articles to the LA

Fox Developer Newsletter one that has been overlooked for

a long time.

You can submit your articles to Barry Lee at CIS# 72723,3422

on Compuserve, or brlee@earthlink.net.

These articles can be on any FoxPro-related topic, whether it

concerns a new technique you’ve discovered, a certain develop-

ment technique you may favor over others, book reviews, etc.

Editor reserves the right to edit or offer constructive comments

concerning submitted articles and accepted articles shall be

considered to be in the public domain.

The quality of this newsletter really depends on the members

that support it, not just read it. And I think we’d all be surprised

by the useful information that could be circulated around the

membership.

So..

How ‘bout it?

(Ed. Note: Todd Landrum is an independent developer in

Evergreen, Colorado. He’s also easily pressured into writing

newsletter articlescg>. He can be reached as

paladin@ecentral .com]

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