The LIMIT = 1 syntax improves the speed when there are potentially a
large number of results from the WHERE clause. Suppose that you are
searching for invoices containing sales of a particular product during
the past month. You may have several thousand invoices, with say 1,000
invoices containing the particular product. The limit clause exits the
count procedure when it finds the first occurrence of the product.
Rather than counting the remaining 999 occurrences, the procedure exits
immediately.
It unfortunately does not increase the speed of "No occurrences".
Albert
On 12/05/2012 12:24 AM, Tony IJntema wrote:
I don’t see how the limit = 1 condition would improve the speed.
Normally the where clause is evaluated from left to right (It depends
on the AND setting).
If the last statement in the where clause is limit = 1, this one is
performed after all other conditions have been met.
So theoretically speaking it would slow down the performance.
As a human being I would use the limit = 1 condition, but I think
that’s the difference between me and my computer
Or do I miss something?
Tony
*From:*[email protected] [mailto:[email protected]] *On Behalf Of
*Javier Valencia
*Sent:* zaterdag 12 mei 2012 4:37
*To:* RBASE-L Mailing List
*Subject:* [RBASE-L] - RE: error message
Jan,
You are correct. I normally use the SELECT (COUNT(…); I have been
gradually changing COMPUTE to SELECT and using, as Albert indicated,
the LIMIT = 1 syntax.
How ironic that the first snippet of code I grab is one with the old
syntax, even when I completely updated the form where that code
resides; I don’t know how I missed that. I need to do a search of all
forms for COMPUTE and update the code.
Javier,
Javier Valencia, PE
O: 913-829-0888
H: 913-397-9605
C: 913-915-3137
*From:*[email protected] <mailto:[email protected]>
[mailto:[email protected]] *On Behalf Of *jan johansen
*Sent:* Friday, May 11, 2012 3:34 PM
*To:* RBASE-L Mailing List
*Subject:* [RBASE-L] - RE: error message
Javier,
Out of curiosity, I'm wondering if your code
-- Check if records are available
COMPUTE vcount AS COUNT equip_code FROM fuel_usage_file +
WHERE equip_code = .vequip_code AND +
fuel_date BETWEEN .vfrom_date AND .vto_date
would operate faster as
SELECT (COUNT(equip_code)) INTO vcount INDIC ivcount +
FROM fuel_usage_file +
WHERE equip_code = .vequip_code AND +
fuel_date BETWEEN .vfrom_date AND .vto_date
Jan
-----Original Message-----
From: "Javier Valencia" <[email protected]
<mailto:[email protected]>>
To: [email protected] <mailto:[email protected]> (RBASE-L Mailing
List)
Date: Fri, 11 May 2012 14:58:21 -0500
Subject: [RBASE-L] - RE: error message
Dan,
Here is a snippet of code I use in similar circumstances. In this
case to display records for a time period:
==========
LABEL Resel
SET VAR vfrom_date DATE = (RDATE(1,1,(IYR(.#DATE))))
SET VAR vto_date DATE = (.#DATE)
--Form date_from_to allows the user to enter a date range. It has
several preset date ranges
EDIT USING date_from_to
-- Check if user slected range or cancelled
IF ( vprint <> 'Y' ) THEN
SET VAR vresel = 'N'
GOTO Done
ENDIF
-- Check if records are available
COMPUTE vcount AS COUNT equip_code FROM fuel_usage_file +
WHERE equip_code = .vequip_code AND +
fuel_date BETWEEN .vfrom_date AND .vto_date
IF ( vcount > 0 ) THEN
BROWSE USING fuel_usage_list WHERE equip_code = .vequip_code AND +
fuel_date BETWEEN .vfrom_date AND .vto_date +
ORDER BY fuel_date DESC, fuel_time DESC
ELSE
PAUSE 2 USING 'No Fuel Usage Records found for this Time
Period...' +
CAPTION 'System Message...' ICON ATTENTION
GOTO Resel
ENDIF
LABEL DONE
CLEAR VAR vcount, vfrom_date, vto_date
RETURN
==========
This approach prevents message displays and informs the user if
records are not available.
I have another approach that as soon as the user selects the time
period, the number of available records is displayed in the same
form; if 0 the user can either cancel or enter a new time period.
Javier,
Javier Valencia, PE
O: 913-829-0888
H: 913-397-9605
C: 913-915-3137
*From:*[email protected] <mailto:[email protected]>
[mailto:[email protected]] <mailto:[mailto:[email protected]]> *On
Behalf Of *Dan Goldberg
*Sent:* Friday, May 11, 2012 1:32 PM
*To:* RBASE-L Mailing List
*Subject:* [RBASE-L] - RE: error message
I will have to change my thought process. I do not like to give
the user the standard error messages....
Dan
*From:* Tony IJntema <mailto:[email protected]>
*Sent:*Friday, May 11, 2012 6:52 AM
*To:*RBASE-L Mailing List <mailto:[email protected]>
*Subject:*[RBASE-L] - RE: error message
As it said, it is a warning not an error.
I assume
Another way to avoid this message is to perform a count on
beforehand, like ‘select count(*) into V_counter indicator
VIND_counter from <tableview> where <clause>’
If V_Counter > 0 then
…
This last option is often used by me, it creates more control in
the application
Tony
*From:*[email protected] <mailto:[email protected]>
[mailto:[email protected]] <mailto:[mailto:[email protected]]> *On
Behalf Of *Dan Goldberg
*Sent:* vrijdag 11 mei 2012 15:23
*To:* RBASE-L Mailing List
*Subject:* [RBASE-L] - error message
I have some code that includes
set messages off
set error messages off
But I still keep getting the warning:
<WARNING> No rows exist or satisfy specified clause (2059)
The only way to turn it off is by using
set error message 2059 OFF
Shouldn’t the “set error messages off” turn off all error messages?
Dan Goldberg
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