On Mon, Jul 13, 2015 at 11:27 PM, Ken Dibble <krdibble@stny.rr.com> wrote:

> Question 1: Does a SQL SELECT place a lock on a VFP .dbf table such that the

> same user can't issue a USE on the table while the query is running?

It will open a table in shared mode. It seemed that a table or an

alias referred by a SQL query was already opened. The SQL query might

have been fired twice by different windows.

A quick-and-dirty solution is to check USED("_table_name_") before

issuing any USE _table_name_! Here is an example:

SELECT 0

IF USED("customer")

SELECT customer

ELSE

USE customer SHARED READONLY

ENDIF

EXECUTE_SQL_QUERY()

You might also consider using USE...AGAIN ALIAS.... in all your SQL queries.

> Question 2: Insofar as possible, should I program defensively by disabling

> controls related to shutting down while queries are running?

Why not use modal windows all the time so that users are always using

one window a time!

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