>What is the fastest way to search through a file to find a substring within a field? I know you can
>

>set filter to 'xyz" $ yourfield
>go top
>

>or an SQL Select equivalent, but in a file where there are thousands of records, it takes a long time, specially on a network...
>
>Is there a quicker way?
>
>Many thanks!

You can not do much.
You can improve the reading, but penalizing the write.
In the sense of building one o more indexes that allows you to pre-select
the data and reduce the number of records where to do thorough research.
In the SQL Server full-text index is a partial solution, in the sense that you find the words, no generic substrings.