Execute the same query twice, get two different results

Question

I have a query that returns two different results:
Oracle Version : 10.2.0.1.0
I am running the following query on the Oracle server in SQL*Plus Worksheet.
SELECT COUNT(*)
FROM AEJOURNAL_S1
WHERE CHAR_TIME BETWEEN TO_DATE('12-AUG-10 01:17:39 PM','DD-MON-YY HH:MI:SS AM') AND
TO_DATE('13-AUG-10 14:17:34','DD-MON-YY HH24:MI:SS')
AND DESC2 LIKE '%'
AND DESC1 LIKE '%'
AND DESC2 LIKE '%'
AND ETYPE LIKE '%'
AND MODULE LIKE '%'
AND LEVELL = '11-WARNING'
ORDER BY ORDD DESC;
The very first time the query is run, it will return a count of 259. The next time the query is run, lets say, 10 seconds later, it will return a count of 260. The above query is exemplary of the kind of thing I'm trying to do. It seems like the more fields filtered against '%', the more random the count return becomes. Sometime you have to execute the query three or four times before it levels out to a consistent number.
I'm using '%' as the default for various fields, because this was the easiest thing to do to support a data-driven Web interface. Maybe I have to 'dynamically' build the entire where clause, instead of just parameterizing the elements and having default '%'. Anyway, to eliminate the web interface for the purpose of troubleshooting the above query was run directly on the Oracle server.
This query runs against a view. The view does a transpose of data from a table.
Below is the view AEJOURNAL_S1
SELECT
CHAR_TIME,
CHAR_INST,
BATCH_ID,
MIN(DECODE(CHAR_ID,6543,CHAR_VALUE)) AS ORDD,
MIN(DECODE(CHAR_ID,6528,CHAR_VALUE)) AS AREAA,
MIN(DECODE(CHAR_ID,6529,CHAR_VALUE)) AS ATT,
COALESCE(MIN(DECODE(CHAR_ID,6534,CHAR_VALUE)),'N/A') AS CATAGORY,
MIN(DECODE(CHAR_ID,6535,CHAR_VALUE)) AS DESC1,
MIN(DECODE(CHAR_ID,6536,CHAR_VALUE)) AS DESC2,
MIN(DECODE(CHAR_ID,6537,CHAR_VALUE)) AS ETYPE,
MIN(DECODE(CHAR_ID,6538,CHAR_VALUE)) AS LEVELL,
MIN(DECODE(CHAR_ID,6539,CHAR_VALUE)) AS MODULE,
MIN(DECODE(CHAR_ID,6540,CHAR_VALUE)) AS MODULE_DESCRIPTION,
MIN(DECODE(CHAR_ID,6541,CHAR_VALUE)) AS NODE,
MIN(DECODE(CHAR_ID,6542,CHAR_VALUE)) AS STATE,
MIN(DECODE(CHAR_ID,6533,CHAR_VALUE)) AS UNIT
FROM CHAR_BATCH_DATA
WHERE subbatch_id = 1774
GROUP BY CHAR_TIME, CHAR_INST, BATCH_ID
So... why does the query omit rows on the first execution? Is this some sort of optimizer issue. Do I need to rebuild indexes? I looked at the indexes, they are all valid.
Thanks for looking,
Dan

Answer 1

user2188367 wrote:
I have a query that returns two different results:
Oracle Version : 10.2.0.1.0
I am running the following query on the Oracle server in SQL*Plus Worksheet.
SELECT COUNT(*)
FROM AEJOURNAL_S1
WHERE CHAR_TIME BETWEEN TO_DATE('12-AUG-10 01:17:39 PM','DD-MON-YY HH:MI:SS AM') AND
TO_DATE('13-AUG-10 14:17:34','DD-MON-YY HH24:MI:SS')
AND DESC2 LIKE '%'
AND DESC1 LIKE '%'
AND DESC2 LIKE '%'
AND ETYPE LIKE '%'
AND MODULE LIKE '%'
AND LEVELL = '11-WARNING'
ORDER BY ORDD DESC;
The very first time the query is run, it will return a count of 259. The next time the query is run, lets say, 10 seconds later, it will return a count of 260. The above query is exemplary of the kind of thing I'm trying to do. It seems like the more fields filtered against '%', the more random the count return becomes. Sometime you have to execute the query three or four times before it levels out to a consistent number.
I'm using '%' as the default for various fields, because this was the easiest thing to do to support a data-driven Web interface. Maybe I have to 'dynamically' build the entire where clause, instead of just parameterizing the elements and having default '%'. Anyway, to eliminate the web interface for the purpose of troubleshooting the above query was run directly on the Oracle server.
This query runs against a view. The view does a transpose of data from a table.
Below is the view AEJOURNAL_S1
SELECT
CHAR_TIME,
CHAR_INST,
BATCH_ID,
MIN(DECODE(CHAR_ID,6543,CHAR_VALUE)) AS ORDD,
MIN(DECODE(CHAR_ID,6528,CHAR_VALUE)) AS AREAA,
MIN(DECODE(CHAR_ID,6529,CHAR_VALUE)) AS ATT,
COALESCE(MIN(DECODE(CHAR_ID,6534,CHAR_VALUE)),'N/A') AS CATAGORY,
MIN(DECODE(CHAR_ID,6535,CHAR_VALUE)) AS DESC1,
MIN(DECODE(CHAR_ID,6536,CHAR_VALUE)) AS DESC2,
MIN(DECODE(CHAR_ID,6537,CHAR_VALUE)) AS ETYPE,
MIN(DECODE(CHAR_ID,6538,CHAR_VALUE)) AS LEVELL,
MIN(DECODE(CHAR_ID,6539,CHAR_VALUE)) AS MODULE,
MIN(DECODE(CHAR_ID,6540,CHAR_VALUE)) AS MODULE_DESCRIPTION,
MIN(DECODE(CHAR_ID,6541,CHAR_VALUE)) AS NODE,
MIN(DECODE(CHAR_ID,6542,CHAR_VALUE)) AS STATE,
MIN(DECODE(CHAR_ID,6533,CHAR_VALUE)) AS UNIT
FROM CHAR_BATCH_DATA
WHERE subbatch_id = 1774
GROUP BY CHAR_TIME, CHAR_INST, BATCH_ID
So... why does the query omit rows on the first execution? Is this some sort of optimizer issue. Do I need to rebuild indexes? I looked at the indexes, they are all valid.
Thanks for looking,
DanIn fact you the first time you ran the query the data has been retrived from disk to memory , in the second time the data is already in memory so the respnse time should be faster ,but if you chagne any condition or column or letter case the optimizer will do the first step (data will be retrived from disk to memory )