Performance Tuning :: Against Count With Group By Clause

Mar 31, 2012

This query is taking 7 hours to execute as I am retrieving data from history table dept_hist.

select count(distinct empid), e.group_nm, d.date,
from emp e, dept_hist d
where e.deptno = d.deptno
and e.up_ts > sysdate -30

[Code]...

Its taking 7 hours to execute.restructing this query.

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PL/SQL :: Count Number Of Employees In Every Department - Group By Clause Not Working

Oct 31, 2012

I have two columns Department and EmpName:

Department EmpName
____________________________________
Sales empname1
Sales empname2
Marketing empname3
Development empname4

Now I want to count the number of employees in every department. I want the output to be

Department Total
______________________
Sales 2
Marketing 1
Development 1

I am retrieving names of the department through a subquery

The query I am trying to execute is:

SELECT Department, Employee FROM
( SELECT ...query from other table) AS Department, count( A.EmpName) AS Employee
FROM Employer A, EmployeeInfo B
WHERE (A.EmpID = B.EmpID AND A.EmpCategory like 'Category2')
GROUP BY Department

I know that you cannot group by using aliases and hence a little work around, but still the query isn't working.

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Performance Tuning :: DECODE In WHERE CLAUSE Performance?

Oct 17, 2011

The following query gets input parameter from the Front End application, which User queries to get Reports.There are many drop down boxes like LOB, FAMILY, BRAND etc., The user may or may not select values from drop down boxes.

If the user select any one or more values ( against each drop down box) it has to fetch all matching values from DB. If the user does'nt select any values it has to fetch all the records, in this case application will send a value 'DEFAULT' (which is not a value in DB ) so that the DB will fetch all the records.

For getting this I wrote a query like below using DECODE, which colleague suggested that will hamper performance.From the below query all the variables V_ are defined in procedure which gets the values selected by user as a comma separated string here V_SELLOB and LOB_DESC is column in DB.

DECODE (V_SELLOB, 'DEFAULT', V_SELLOB, LOB_DESC) IN
OPEN v_refcursor FOR
SELECT /*+ FULL(a) PARALLEL(a, 5) */
*
FROM items a
WHERE a.sku_status = 'A'

[code]...

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Performance Tuning :: Check Count For Each Partition?

May 2, 2012

We have 525 partitions and we want find out partition wise total count. finding partitionwise count in a particular table.

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Performance Tuning :: How To Avoid Repeat Where Clause In Oracle Sql

Jun 4, 2013

avoid duplication of **where** clause in my query.

In my below query, **JOIN** condition is same for both the queries and **WHERE** condition also same except this clause "and code.code_name="transaction_1" In **IF ** condition only credit and debit is swapped on both queries, due to this **Credit and Debit** and this where clause "and code.code_name="transaction_1" I am duplicating the query. avoid this duplication. I am using oracle 11g

SELECT day AS business_date,
SUM(amount) AS AMOUNT,
type_amnt AS amount_type,

[Code]....

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Performance Tuning :: How To Overcome Rownum Clause From Select

Dec 27, 2010

high number of executions of specific types of queries which is using only rownum clause. For exam.

select ani, rowid from tbl_smschat_upuor where rownum<=:"SYS_B_0";

DB is having high number of executions of these type of queries and these when I m checking the execution plan for the same type of queries it is accessing the full table scan.

======================execution plan for above query
1000 rows selected.
Execution Plan
----------------------------------------------------------
Plan hash value: 91289622
--------------------------------------------------------------------------------

[code]....

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Performance Tuning :: Query Using Row Num In Where Clause With Millions Of Records

Dec 8, 2010

There is a table in Database with millions of records and a query --- Select rowid, ANI, DNIS, message from tbl_sms_talkies where rownum<=:"SYS_B_0" ---- using the high CPU and also this query having high number of executions.

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Performance Tuning :: Collection Count High In Memory

Feb 13, 2013

I have two tables with same columns(15 of them), I am trying to find difference between two tables using minus operator and then insert in stage table using below code

Issue is table1 has 50 million records
table2 is empty

so when first time when we execute this v_collection1,v_collection2 collection will have 50 million records in it which will go in memory, I think this is not good, because going in memory will eat memory and resources while sorting and other activities ?

After fetching records in collection we are inserting that in stage table and then COMMIT so i think that wont be good because committing 50 million will generate large amount of redo?

below is snippet of my code

DECLARE
type lst_collection1
IS
TABLE OF table1.col1%type INDEX BY binary_integer;
type lst_collection2
IS
[code].......

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Performance Tuning :: Full Table Scan - Query Without Where Clause?

Jul 11, 2013

Below query is degrading the performance of database. As we know that, without where clause, query do full table scan.Now, it is written to generate the sequence no.

SQL> explain plan for
2 SELECT NVL(MAX(P.NUM_SERIAL_NO), 0) + 1 FROM CNFGTR_IRDA_ENVELOPE_DTLS P
3 /
Explained.
SQL> select * from table(dbms_xplan.display());
PLAN_TABLE_OUTPUT
----------------------------------------------------------------------------------------------------
Plan hash value: 3345343365
------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
------------------------------------------------------------------------------------------------

[code].....

Index is not created on the column.

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Performance Tuning :: Pass 4000 - 5000 Parameter In IN Clause?

Mar 2, 2011

In my below query example , i have to pass more than 4000-5000 paramter in "a1.num" in below query. what is the best way to handle this, also if I pass more than 2000 paramter , the query takes a long time to execute. How can we solve the performance issue as well how I can pass more parameter.

SELECT c1, c2,
TO_CHAR (c3, 'HH24:MI'),
c4,
c5,

[code]...

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Performance Tuning :: How To Tune Order By Clause Without Changing Sort Area

May 1, 2008

How to avoid sort operation by an order by clause without changing the sort area size.what hints or changes should be done in query so that order by clause work faster.

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Performance Tuning :: Index Usage In Order By Clause On Nullable Column

Jan 28, 2011

I came across situation where a Nullable column is not using index for 'order by' clause. I added Not Null condition in the 'where' condition but it wasn't useful. I don't wanted to make composite index with not nullable column or with constant or modify column to 'Not Null'

So I carried out test cases and during which I found that in one case the sql statement does 'fast full scan' for data access but does not use index for 'order by' sorting

here are the steps

Initially I kept the column Nullable

SQL> create sequence s5;
Sequence created.

SQL> create table t5 as select s5.nextval id,a.* from dba_objects a where rownum<1001;
Table created.

SQL> set pages 100
SQL> select column_name,nullable from user_tab_columns where table_name='T5';

SQL> create index i5 on t5(id);
Index created.

SQL> exec dbms_stats.gather_table_stats(user,'T5',cascade=>true);
PL/SQL procedure successfully completed.
exit

SQL> alter session set events '10046 trace name context forever, level 12';

select *
from
t5 where id is not null order by id

call count cpu elapsed disk query current rows
------- ------ -------- ---------- ---------- ---------- ---------- ----------
Parse 1 0.00 0.00 0 0 0 0
Execute 1 0.00 0.00 0 0 0 0
Fetch 68 0.00 0.00 0 16 0 1000
------- ------ -------- ---------- ---------- ---------- ---------- ----------
total 70 0.01 0.00 0 16 0 1000

Misses in library cache during parse: 1
Optimizer mode: ALL_ROWS
Parsing user id: 5

Rows Row Source Operation
------- ---------------------------------------------------
1000 SORT ORDER BY (cr=16 pr=0 pw=0 time=4771 us)
1000 TABLE ACCESS FULL T5 (cr=16 pr=0 pw=0 time=1157 us)

Elapsed times include waiting on following events:
Event waited on Times Max. Wait Total Waited
---------------------------------------- Waited ---------- ------------
SQL*Net message to client 68 0.00 0.00
SQL*Net message from client 68 49.49 49.72
********************************************************************************

select /*+ index(t i5) */ *
from
t5 t where id is not null order by id

call count cpu elapsed disk query current rows
------- ------ -------- ---------- ---------- ---------- ---------- ----------
Parse 1 0.00 0.00 0 0 0 0
Execute 1 0.00 0.00 0 0 0 0
Fetch 68 0.00 0.00 0 150 0 1000
------- ------ -------- ---------- ---------- ---------- ---------- ----------
total 70 0.00 0.00 0 150 0 1000

Misses in library cache during parse: 1
Optimizer mode: ALL_ROWS
Parsing user id: 5

Rows Row Source Operation
------- ---------------------------------------------------
1000 TABLE ACCESS BY INDEX ROWID T5 (cr=150 pr=0 pw=0 time=5167 us)
1000 INDEX FULL SCAN I5 (cr=71 pr=0 pw=0 time=3141 us)(object id 4673065)

Elapsed times include waiting on following events:
Event waited on Times Max. Wait Total Waited
---------------------------------------- Waited ---------- ------------
SQL*Net message to client 69 0.00 0.00
SQL*Net message from client 69 22.89 28.04

Now I modified the 'id' column to Not Null

SQL> alter table t5 modify id not null;

SQL> set pages 100
SQL> select column_name,nullable from user_tab_columns where table_name='T5';

COLUMN_NAME N
------------------------------ -
ID N
OWNER Y
OBJECT_NAME Y
SUBOBJECT_NAME Y
OBJECT_ID Y
DATA_OBJECT_ID Y
OBJECT_TYPE Y
CREATED Y
LAST_DDL_TIME Y
TIMESTAMP Y
STATUS Y
TEMPORARY Y
GENERATED Y
SECONDARY Y

14 rows selected.

select *
from
t5 order by id

call count cpu elapsed disk query current rows
------- ------ -------- ---------- ---------- ---------- ---------- ----------
Parse 1 0.00 0.01 0 29 0 0
Execute 1 0.00 0.00 0 0 0 0
Fetch 68 0.00 0.00 0 16 0 1000
------- ------ -------- ---------- ---------- ---------- ---------- ----------
total 70 0.01 0.01 0 45 0 1000

Misses in library cache during parse: 1
Optimizer mode: ALL_ROWS
Parsing user id: 5

Rows Row Source Operation
------- ---------------------------------------------------
1000 SORT ORDER BY (cr=16 pr=0 pw=0 time=2398 us)
1000 TABLE ACCESS FULL T5 (cr=16 pr=0 pw=0 time=1152 us)

Elapsed times include waiting on following events:
Event waited on Times Max. Wait Total Waited
---------------------------------------- Waited ---------- ------------
SQL*Net message to client 68 0.00 0.00
SQL*Net message from client 68 37.74 37.91
********************************************************************************

select /*+ index(t i5) */ *
from
t5 t order by id

call count cpu elapsed disk query current rows
------- ------ -------- ---------- ---------- ---------- ---------- ----------
Parse 1 0.00 0.00 0 0 0 0
Execute 1 0.00 0.00 0 0 0 0
Fetch 68 0.00 0.00 0 150 0 1000
------- ------ -------- ---------- ---------- ---------- ---------- ----------
total 70 0.00 0.00 0 150 0 1000

Misses in library cache during parse: 1
Optimizer mode: ALL_ROWS
Parsing user id: 5

Rows Row Source Operation
------- ---------------------------------------------------
1000 TABLE ACCESS BY INDEX ROWID T5 (cr=150 pr=0 pw=0 time=4166 us)
1000 INDEX FULL SCAN I5 (cr=71 pr=0 pw=0 time=3142 us)(object id 4673065)

Elapsed times include waiting on following events:
Event waited on Times Max. Wait Total Waited
---------------------------------------- Waited ---------- ------------
SQL*Net message to client 68 0.00 0.00
SQL*Net message from client 68 8.28 8.45

select id
from
t5 order by id

call count cpu elapsed disk query current rows
------- ------ -------- ---------- ---------- ---------- ---------- ----------
Parse 1 0.00 0.00 0 0 0 0
Execute 1 0.00 0.00 0 0 0 0
Fetch 68 0.00 0.00 0 6 0 1000
------- ------ -------- ---------- ---------- ---------- ---------- ----------
total 70 0.00 0.00 0 6 0 1000

Misses in library cache during parse: 1
Optimizer mode: ALL_ROWS
Parsing user id: 5

Rows Row Source Operation
------- ---------------------------------------------------
1000 SORT ORDER BY (cr=6 pr=0 pw=0 time=1342 us)
1000 INDEX FAST FULL SCAN I5 (cr=6 pr=0 pw=0 time=1093 us)(object id 4673065)

Elapsed times include waiting on following events:
Event waited on Times Max. Wait Total Waited
---------------------------------------- Waited ---------- ------------
SQL*Net message to client 68 0.00 0.00
SQL*Net message from client 68 1.88 1.89

Questions are

1) Why adding 'where id is not null wasn't enough for the index to get used in 'order by'?
2) While we got 'fast full scan' why index wasn't used for 'order by' clause?
3) Do we need the indexed column in where clause for being used in 'order by clause' too?
4) Do we need 'order by' clause if we are selecting only the indexed column with sequence generated values?

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Performance Tuning :: Where Filter Result Rows Save Before Join And Group By Operation

Jul 7, 2012

Where filter middle_rows save before join and grop by operation?

It is save rows in PGA Private SQL Area or save blocks in SGA databuffer?

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Group Records With Less Than One Hour Separation And Count How Many Per Group

Nov 1, 2013

I'm trying to group sets of data based on time separations between records and then count how many records are in each group.

In the example below, I want to return the count for each group of data, so Group 1=5, Group 2=5 and Group 3=5

SELECT AREA_ID AS "AREA ID",
LOC_ID AS "LOCATION ID",
TEST_DATE AS "DATE",
TEST_TIME AS "TIME"
FROM MON_TEST_MASTER
WHERE AREA_ID =89
AND LOC_ID ='3015'
AND TEST_DATE ='10/19/1994';

[code]....

Group 1 = 8:00:22 to 8:41:22

Group 2 = 11:35:47 to 11:35:47

Group 3 = 15:13:46 to 15:13:46

Keep in mind the times will always change, and sometime go over the one hour mark, but no group will have more then a one hour separation between records.

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SQL & PL/SQL :: Get Count On Group And Total Count For Each Group

Mar 23, 2013

I'm using this code, and it performs fine, but I'm wondering if there is a more elegant way to do it--maybe with "ROLLBACK". Basically (as you can see) I need to get a normal count for each group but also for each group take a percentage of the total count (so all groups pct adds up to 100 (oh yeah, don't test for zero below, but just a test... )

select
c.Event,
c.code,
count(1) as calls,
total.total_count,
count(1) / total.total_count * 100 as pct_of_total
from
table1 c

[Code]....

[Edit MC: add code tags, do it yourself next time]

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Performance Tuning :: Index 15 Columns When Cannot Predict Columns Will Be Used In Where Clause?

Apr 4, 2011

I am running a fairly busy Oracle 10gR2 DB, one of the tables has about 120 columns and this table receives on average 1500 insertions per second. The table is partitioned and the partitioning is based on the most important of the two timestamp columns. There are two timestamps, they hold different times.

Out of these 120 columns, about 15 need to be indexed. Out of the 15 two of them are timestamp, at least one of these two timestamp columns is always in the where clause the queries.

Now the challenge is, the queries we run can have any combination of the 13 other columns + one timestamp. In reality the queries never have more than 7 or 8 columns in the where clause but even if we had only 4 columns in the where clause we would still have the same problem.

So if I create one concatenated index for all these columns it will not be very efficient because after the 4th or 5th column the sorting would no longer be very useful and I believe the optimiser would simply not use the rest of the index. So queries that use the leading columns of the index in sequence work well, but if I need to query the 10th column the I have performance issues.

Now, if I create multiple single column indexes oracle will have to work a lot harder to maintain all these indexes and it will create performance issues (I have tried that). Besides, if I have multiple single column indexes the optimiser will do nested loops twice or three times and will hit only the first few columns of the where clause so I think it will kind of be the same as the long concatenated index.

What I am trying to do is exactly what the Bitmap index would do, it would be very good if I could use the AND condition that a Bitmap index uses. This way I could have N number of single column indexes which the optimiser could pick from and serve the query with exactly the ones it needs. But unfortunately using the Bitmap index here is not an option given the large amount of inserts that I get on this table.

I have been looking for alternatives, I have considered creating multiple shorter concatenated indexes but this still would not address the issue since many queries would still not be served properly and therefore would take a very long time to complete.

What I had in mind would be some sort of multidimensional index, I am not even sure if such thing exists. But essentially it would be some sort of index that could serve a query efficiently regardless of the fact that the where clause has the 1st, 3rd and last columns of the index.

So considering how widely used Oracle is and how many super large databases there are out there, this problem must be common.

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SQL & PL/SQL :: Group By Clause

Mar 31, 2011

This time, I am going to provide the DML statements.

I have a simple table with 3 fields in it.I want to group by ACCT_NUMBER and sum of BALANCE field. But I want to get the description of the first row in a group.

the statements below. Here there are two groups of records 2001 and 2002. My sql(which I am working on) should return the following :

2001 EMPL TRAINING-MIS 20
2002 OTHER PROF SERV-HR 40

The following query will group by ACCT_NUMBER and sum of the BALANCE field. But how can I get the DESCRIPTION?

SELECT ACCT_NUMBER, SUM(BALANCE)
FROM TEST
GROUP BY ACCT_NUMBER
CREATE TABLE "TEST"
("ACCT_NUMBER" VARCHAR2(20 BYTE),
"DESCRIPTION" VARCHAR2(20 BYTE),

[code]...

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SQL & PL/SQL :: Group By For Getting Count

Mar 7, 2013

I need suing group by for getting count.I have a table with columns below

SYS_AUDIT_IDSYS_AUDIT_PROG_IDPROG_FINDING_ID_COUNT

178921652
178921641
178921631
179321521
179321511
179321501
179321491
179321461

I want to count number of SYS_AUDIT_PROG_ID for each audit and count of PROG_FINDING_ID_COUNT

I want to get
1789 3 4

I tried this query but this is not working

[code]select sys_audit_id ,count (sys_audit_prog_id), count(prog_finding_id_count) from

my_table sub
group by sys_audit_id [/code]

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SQL & PL/SQL :: How To Increment Count When GROUP By Is Used

Feb 17, 2010

SNO column should be incremented depending upon the total records to be fetched.if i get 4 records then sno numbers should be 1,2,3,4.i dont want to put rownum also in the GROUP BY clause.how to increment the serial number?

SELECT JC.A,
ROWNUM SNO, --serial number
JC.B,
SUM(CHR.AMOUNT),
SUM(CHR.FINALAMOUNT),
JC.C,
JC.D,
C.E,
JC.F,
JC.G
FROM CHARGES CHR
WHERE JC.B = '12111'
AND JC.STATUS = 'INVOICED'
GROUP BY JC.A, JC.B, JC.C, JC.D, JC.E, JC.F, JC.G;

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Count And Group Query?

Apr 23, 2012

I have a report I created and I need to get a Total Count by Plan Code Description for Each State. I do this and get all my data:

SELECT
mv.R1_State,
mv.subscriber_id,
mv.plan_code,
pm.description,
mv.line_of_business,

[code]...

But I cannot get the count I have to do a separate Query to get the count here it is How can I put the two together to get my count information and Report information together in one Report???

Select
Count(pm.description),
mv.R1_State
FROM windsoradm.member_mv mv

[code]....

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PL/SQL :: Count / Group By Between Dates

Oct 30, 2013

I am trying to count the number of IDs dropped and enrolled in each unit for each of the 4 terms between their perspective dates. There are 4 Terms and an ID can participate in a unit in any of these terms:

TERMSTART_DATEEND_DATE125-Feb-1318-Mar-13227-May-1317-Jun-13326-Aug-1316-Sep-13425-Nov-1316-Dec-13 .

I am trying to count how many IDs enrolled in a unit between those dates and how many doped before the end dateThe ENROL_DATE for each ID in a unit has to be between the given Term Dates to count. Unit KIS has 1 ENROL and one DROP in TERM 1 UNIT POL occurs in TERM 2 and 4 and both DROPUNIT LIN and 1 ENROL and 1 DROP in 2 different TERMS My problem is how do i specify count ENROL and count drop between the Term dates and then group by TERM and UNIT. 

{code}CREATE TABLE DAN_GR4(ID             NUMBER(12),STATUS           VARCHAR2(12),TERM             NUMBER(12),ENROL_DTE       DATE,TERM_START_DTE  DATE,TERM_END_DATE   DATE,UNIT            VARCHAR2 (12));  INSERT INTO  DAN_GR4 (ID,STATUS,TERM,ENROL_DTE,TERM_START_DTE,TERM_END_DATE,UNIT) VALUES ('1',    'ENROL'    ,'1',    '15-Mar-13'    ,'25-Feb-13' ,'18-Mar-13',  'KIS');INSERT INTO  DAN_GR4 (ID,STATUS,TERM,ENROL_DTE,TERM_START_DTE,TERM_END_DATE,UNIT) VALUES ('1',    'DROP'    ,'2',    '27-MAY-13'    ,'27-MAY-13' ,'17-JUN-13',    'POL');INSERT INTO  DAN_GR4 (ID,STATUS,TERM,ENROL_DTE,TERM_START_DTE,TERM_END_DATE,UNIT) VALUES ('1',    'DROP'    ,'2',    '27-JUN-13'    ,'27-
[code].....

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Count / Group Not Working?

Dec 1, 2007

I am using oracle, and have the following relations.

Patient(Patno, name,docno*)
Doctor(Docno, name, specialization)
Treatment(treatno, startdate, reason, docno*, patno*)

I want to list every patients number and name, and the number of treatments given by a certain doctor (e.g doctor name = 'smith'). the problem i am having is that if i specify the doctor is WHERE clause it only gives me the doctors who are under 'smith' but i want all even if 'smith' has given them 0 treatments. below is code that i have so far to view all patients with corresponding data.

select pa.patno, pa.lname, tr.treatno
from patient pa full join treatment tr on tr.patno=pa.patno;

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SQL & PL/SQL :: Expression Column With A Group By Clause?

Mar 28, 2011

getting expression into a Group By query in oracle.

I have a simple table with two columns. 'ID' and 'Amount'

I want output of the SQL to the following (only 2 fields in the output): I have attached the desired output.

select sum(amountheld) from table1
where member_status = 'MEMBER'
group by ID

This group by query works. But how can i get the expression field (the first field which 'TEMPACCOUNT') in this query (based on my attached output).

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SQL & PL/SQL :: Analytical Function Instead Of Group By Clause?

Sep 18, 2012

I want to use Analytical function instead of group by clause for below query..

select
CASE
WHEN ADMT.SOURCESYSTEM ='CLU'
THEN COUNT(ADMT.TOTAL_COUNT)*5
ELSE COUNT(ADMT.TOTAL_COUNT)
END TOTAL_COUNT
from ESMARTABC.ABC_DRVR_MFAILS_TMP ADMT
group by ADMT.SOURCESYSTEM

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SQL & PL/SQL :: Can Group BY Clause Have Expression Field

Apr 4, 2011

Can Group BY clause have an expression field?

Say for example, I want to group by the fields "Type" and and expression called "expression" (which is a case statement). I tried running this query and it says "expression" is invalide identifier.

select type, case when SUBSTR (glnumber, 1, 2) = '05' then 'IS'
when SUBSTR (glnumber, 1, 2) = '06' then 'IS'
else 'BS'
end "expression" , sum(balance)
from table
group by TYPE, "expression"

If there is any online material on how to GROUP BY on an expression(like above)

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Group By Multiple Columns / Count And Then Find A Max

May 24, 2008

I have three tables,let's say

table stores
sid | store_name
1 | one
2 | two
3 | three

table products
pid | sid | p_name
1 | 2 | pone
2 | 2 | ptwo
3 | 3 | pthree

table sales
said | sid | pid
1 | 2 | 1
2 | 3 | 1
3 | 2 | 2
4 | 1 | 3
5 | 2 | 2
6 | 3 | 2
7 | 3 | 2

and i want display the product that sells best in every store. I try to group by multiple columns counting how many times each product was sold in every store, but don't know how to select the one which was best sold (maximal number of times)

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SQL & PL/SQL :: Group By Count And Date Time Range

Feb 3, 2011

We have a table with timestamp column and having millions of records.We want to create a materialized view or query, which can give count based

-on some group by columns from table and
-group by on condition (if count > 1000) and
-group by on condition (if timestamp range for that group is > 1hr)

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Performance Tuning :: Tools For Database Tuning And Instance Tuning

Jul 12, 2010

Looking to understand the difference between instance tuning and database tuning.

What is the difference between these two tuning exercises? I understand that an instance is memory based structures (logical) where as database consists of physical structures.

However, how does one tune a database the physical structure? Does it have to do with file placements/block sizes etc. Would you agree that a lot of that is taken care by ASM now in 11g? What tools are required/available (third party as well as oracle supplied) for these types of tuning scenarios?

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Performance Tuning :: Merge Statement Tuning For 100M Records In Table?

Oct 31, 2011

I have two tables with 113M records in DWH_BILL_DET & 103M in prd_rerate_chg_que and Im running following merge query, which is running for 13 hrs to update records, which is quiet longer time.

SQL> explain plan for MERGE /*+ parallel (rq, 16) */
INTO DWH_BILL_DET rq
USING (SELECT rated_que_rowid,
detail_rerate_flag_code,
rerate_sel_key,

[code].....

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Performance Tuning :: How Length Of Column Width Effects Index Performance

Sep 30, 2010

How the length of column width effects index performance?

For example if i had IOT table emp_iot with columns:
(id number,
job varchar2(20),
time date,
plan number)

Table key consist of(id, job, time)

Column JOB has fixed list of distinct values ('ANALYST', 'NIGHT_WORKED', etc...).

What performance increase i could expect if in column "job" i would store not names but concrete numbers identifying job names.
For e.g. i would store "1" instead 'ANALYST' and "2" instead 'NIGHT_WORKED'.

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