On Mon, Jul 13, 2015 at 11:27 PM, Ken Dibble <[email protected]> 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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