SQL & PL/SQL :: What Should Be Order Of Columns While Creating B-tree Non-unique Index
Jul 19, 2012What should be the order of columns while creating b-tree non-unique index.
Low cardinality first
or
Hight cardinality first
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SQL & PL/SQL :: Table With A Non-unique Index Consisting Of Three Columns
Sep 13, 2013I have a table with a non-unique index consisting of three columns. The first column is not null while the remaining two are nullable. Queries using this index will chiefly be made in two ways.
1. Column one and two having values. Column three is null.
2. Column one and thre having values. Column two is null.
In both cases I expect range scan will be used since it's non-unique. In the first case the scan will be on values in column one and two. But what happens in case two. Will the range be on colum one, column two(being null) and cxolumn three? Or will it be on just column one since the second column is null? I have done some testing. I can see , using EXPLAN PLAN, that range scan is used in both cases. how the index is used?
Is there any other drawbacks with an index like this?
Non Unique Index Using A Non Unique Field
Aug 14, 2013Using Oracle 11g, below is the table, partitions, unique and non-unique local index:
CREATE TABLE DOCA( DOCA_ID NUMBER NOT NULL , DOCA_BKG_PAX_ID NUMBER NULL , ROW_PURGE_DATE DATE NULL ,)PARTITION BY RANGE(ROW_PURGE_DATE)INTERVAL(NUMTOYMINTERVAL(1, 'MONTH'))( PARTITION P2007 VALUES LESS THAN (TO_DATE('01/01/2008', 'dd/mm/yyyy')), PARTITION P200801 VALUES LESS THAN (TO_DATE('01/02/2008', 'dd/mm/yyyy')),) TABLESPACE T0; ALTER TABLE DOCA ENABLE ROW MOVEMENT;
CREATE UNIQUE INDEX XPKDOCA ON DOCA( DOCA_ID ASC, ROW_PURGE_DATE ASC)LOCALREVERSE TABLESPACE I0; ALTER TABLE DOCA ADD CONSTRAINT XPKDOCA PRIMARY KEY (DOCA_ID); CREATE INDEX XFKDOCA_DOCA_BKG_PAX_ID ON DOCA( DOCA_BKG_PAX_ID ASC)LOCALREVERSETABLESPACE I0;
I would like to know the difference between the performance of the unique and non-unique local indexes?.
SQL & PL/SQL :: Bitmap Or B-Tree Index?
Apr 9, 2010I was executing following query and it was taking about 20 sec's to execute before i decided to create B-Tree(Normal) index on column DeliVery.
Select
DeliVery,Code,Sum(Units),Sum(Loads),Count(units),
Count(Loads)
Where
[code]...
After creating B-Tree index on Column Delivery the execution time has been reduced to one second ,thats what i wanted. But If i create Bitmap index on the same column then execution time is not getting reduced and is still same around 20 sec.I think theoratically "Delivery" column is the right candidate for Bitmap index? whether should i create bitmap index or stick with B-Tree index?
SQL & PL/SQL :: Error For Creating Tree Structure - Not Showing All Records
Mar 1, 2013I have one table test_pc :
EVENT_IDPARENT_EVENT_ID
2001
2002 2001
1001 2002
1002 1001
1004
1003 2005
1006
Scripts are mentioned below :
create table test_pc
(event_id number(10), parent_event_id number(10));
insert into test_pc values(2001,null);
insert into test_pc values(1006,null);
insert into test_pc values(1004,null);
insert into test_pc values(2002,2001);
insert into test_pc values(1001,2002);
insert into test_pc values(1002,1001);
insert into test_pc values(1003,2005);
In order to derive parent child relationship I have ran the following query :
select *
from test_pc
start with parent_event_id is null
connect by nocycle prior event_id = parent_event_id;
It is giving all the records except the last one (i.e. event_id = 1003 and parent_event_id = 2005), because the parent_event_id does not exists in the table.
But my requirement is to show all the record, i.e. if the parent_child relationship is present then show accordingly and also show the rest of the records where the parent_child does not exists even the parent_event_id exists.
Application Express :: Creating Tree With Multiple Tables?
Jun 20, 2012I want to do a tree view based on the following tables in APEX:
create table plattform (
id number,
name varchar2(200))
create table environment (
id number,
plattform_id number,
name varchar2(200))
[code].....
B-Tree Index On Column - Local Or Global
Feb 20, 2013Version Info: 11.2 on Solaris 10
I have a partitioned table like below. I want to create a B-Tree index on SALES_RGN column which is neither the part of Primary key or the Partitioned key. Should I create this index as local or Global ?
CREATE TABLE sales_dtl
(
txn_id number (9),
salesman_id number(5),
salesman_name varchar2(30),
sales_rgn varchar2(10), -----------------------------> This column needs to be indexed
sales_amount number(10),
sales_date date,
constraint pk_sales_dtl primary key (txn_id)
[code]....
Performance Tuning :: Index 15 Columns When Cannot Predict Columns Will Be Used In Where Clause?
Apr 4, 2011I 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.
Creating Unique Constraint That Excludes Null
May 22, 2013I have a table where I want user to fill in unique values for a field which is easy to do.
Problem is sometimes the values can be null so an ordinary unique constraint does not work because multiple null records. Is there a way of validating only non null values to ensure all data entered that is non null is unique?
SQL & PL/SQL :: Unique Index Shorting
Jun 18, 2012I have a running application where i have a table with pk defined on it and the pk clumn is inde in asc order by default. Can i alter the index in desc order as i always need to see the data in desc order.
View 7 Replies View RelatedSQL & PL/SQL :: How To Add Column In Unique Index
Jan 17, 2011I have created one unique index on one column of my table. Now i would like to add one more column in the same index without dropping the index.
SQL > CREATE TABLE DEBUG_TABLE
2 (
3 SLNO NUMBER,
4 MESSAGE VARCHAR2(4000 BYTE),
5 CREATED_DATE DATE DEFAULT SYSDATE,
6 CREATED_TIME TIMESTAMP(6) DEFAULT SYSDATE
7 );
Table created.
SQL > CREATE UNIQUE INDEX index_debug1 ON debug_table (SLNO);
Index created.
SQL > ALTER INDEX index_debug1 ADD COLUMN MESSAGE;
ALTER INDEX index_debug1 ADD COLUMN MESSAGE
*
ERROR at line 1:
ORA-02243: invalid ALTER INDEX or ALTER MATERIALIZED VIEW option
SQL >
SQL & PL/SQL :: Update Each Row - Unique Index
Jun 23, 2011I've got a table which has no unique identifier for a row. I have a field for an ID value but somhow there are duplicate values in this field.
Now I want to create an unique index over this field but therefore I have to remove the duplicate values.
So what I need is an update statement, maybe in a for each loop, which updates the ID field in each row starting with 1 and increasing the value.
In Informix there is a rowid value which is automatically set by Informix. But I think there´s no correspondent function/value in Oracle....
SQL & PL/SQL :: Creating Composite Unique Key With Only 1 Column Allowed To Be Changed
Jul 3, 2013I have a table say MY_TAB with columns as below
emp_id number,
name varchar2(30),
from_dt date,
remarks varchar2(60)
insert into MY_TAB values (1,'TOM','01-JAN-13', 'some remark');
insert into MY_TAB values (1,'TOM','02-JAN-13', 'some remark');
insert into MY_TAB values (2,'TOM','01-JAN-13', 'some remark');
insert into MY_TAB values (3,'TOM','01-JAN-13', 'some remark');
insert into MY_TAB values (4,'TOM','01-JAN-13', 'some remark');
insert into MY_TAB values (4,'TOM','02-JAN-13', 'some remark');
How do I ensure that when a user tries to insert record with emp_id as 1, then he should only be allowed to enter another from_dt but the value in the name column have to be the same as in the previous row of emp_id 1.
insert into MY_TAB values (1,'TOOM','03-JAN-13') --shld not be allowed.
Unique Function Based Index
Jun 27, 2011I have a table which sees a lot of use for queries
CREATE TABLE CASE_STAGE
(
ID NUMBER(9) NOT NULL,
STAGE_ID NUMBER(9) NOT NULL,
CASE_PHASE_ID NUMBER(9) NOT NULL,
"CURRENT" NUMBER(1) NOT NULL,
--and other columns
)
ID is a primary key
CASE_PHASE_ID is a foreign key
"CURRENT" should only ever have values of 0 or 1. When it has a value of 1 it is unique for that CASE_PHASE_ID
What I have tried that doesn't work is
create unique index case_stage_F_IDX1 on case_stage("CURRENT", case_Phase_id) which gives me
ORA-01452: cannot CREATE UNIQUE INDEX; duplicate keys found
What is the correct syntax, something like ("CURRENT"=1,case_phase_id) seems right but fails with an error about a missing bracket. Do I need to use a CASE statement here?
How To Create Unique Index On A View
Aug 24, 201211.2.0.1...How do I create an index on a view or any workaround that my view won't get duplicates?
SQL> create unique index indx01 on db_backup_details_vw(id);
create unique index indx01 on db_backup_details_vw(id)
*
ERROR at line 1:
ORA-01702: a view is not appropriate here
Can Create Unique Index On Subset Of Record
Apr 9, 2013I have following records in table (T)
Idtype_cdNbrDt
1A1001/1/2013
2A101Null
3B100Null
4C100Null
5A100Null
Based on the type-cd, I need to create Unique index on Nbr & Dt columns
In above record set, I want to create Unique index on type_cd=A and not on B&C (Here i expect duplictes for a combination of Nbr & Dt)
Can we create Unique index on subset of record?
SQL & PL/SQL :: Duplicated Entries In A Valid Unique Index?
May 26, 2010I'm having problem with my database, which contains more than 1 rows with a same value on a field that has uniqueness contraint.
Here is the log from sqlplus. When I select on RI field, it shows 2 rows. But when I select on SCNUM field, it shows only 1 row. This SCNUM has an unique index on it.
And it is still in VALID state
SQL> set autotrace on
SQL> select ri, scnum from scratch1_p where ri in (536964983, 536955574);
select ri from scratch1_p where scnum='444393975';
RI SCNUM
---------- ----------
536955574 444393975
[code].....
Performance Tuning :: Force Index Unique Scan?
Jun 14, 2012Is there any hint to force "Index Unique Scan" over "Index Range Scan".
My query is generating different plans with the above two, and very slow when it uses "Index Range Scan".
When Inserting Data Unique Index Initially In Unusable State
Apr 9, 2013We are getting an error as below when trying to load data into a table.
INSERT /*+ APPEND parallel(IA_SBSCR_DED_MAX,4) */ INTO EDW.IA_SBSCR_DED_MAX
*
ERROR at line 1:
ORA-12801: error signaled in parallel query server P000
ORA-26026: unique index EDW.XPKIA_SBSCR_DED_MAX_A initially in unusable state
The index has been rebuilt but we still have this issue.
9.2.0.8.0 Oracle Index Not Used In Order By Desc?
Oct 30, 2011There are 2 setup of Oracle DB 9.2.0.8.0. There is a table T1 in both (one that is working 6.5 million rows and the other that is not working having 6.7 million rows). while doing - select * from t1 order by c1 desc; one is using index i1 and other is going for full table access.
View 1 Replies View RelatedSQL & PL/SQL :: Changing Order Of Columns?
Apr 30, 2012i have a table test on 4 different-different database, at the starting structure is same in all the database. and now i want to change the datatype of the primary key column named "testid" , then i add a temp column in test table (and it is added at the last in table).
i have copied the data of testid in temp column and renamed it as testid and i dropped the testid column , then the problem is that primary key column will comes at last and i want to make it like previous position so that there will not be any difference in all 4 database as in structure.
is it possible to changing column order as our desire without dropping the table?and i made all the script to changing the datatype of primary key column.
SQL & PL/SQL :: Order By Multiple Columns
Oct 9, 2013I have a query to pull the first contact of students.
The table has all contacts like parent/guardian, friends family, emergency contact etc.
I would like to the first primary contact in this order,
1. initial contact, 2. same as student address and also have to be parents,
3. live with and also a parent, 4. parents 5. friends.
I don't know how to pull 2 and 3 . because it looks like it needs to concatenate the columns.
here is my initial query
Select Min(U2.Id) Keep (Dense_Rank First Order By U2.Initial_Contact Desc, U2.Same_As_Students_Address Desc,u2.lives_with DESC,U2.Guardian Desc)
From Contacts
how to achieve 2 and 3?
The table script is attached. All the above columns are 1 or 0.
SQL & PL/SQL :: Date Format - Do (ORDER BY) By Concatenating Two Columns?
Jun 26, 2013 I want to do 'ORDER BY' by concatenating the two columns(date +varchar2).But not working and geting the error - ORA-01855: AM/A.M. or PM/P.M. required
SQL> create table dat2 (
mod_date date,
am_pm varchar2 (10) ) ; 2 3
Table created.
SQL> INSERT INTO DAT2 ( MOD_DATE, AM_PM ) VALUES (
TO_Date( '06/05/2003 12:00:00 AM', 'MM/DD/YYYY HH:MI:SS AM'), '7:25AM'); 2
1 row created.
[code]...
ERROR at line 2:
ORA-01855: AM/A.M. or PM/P.M. required
SQL & PL/SQL :: Does Ascending Index Ensures That Query Without Order By Will Have Result Set Sorted
Jul 4, 2013Does ascending index ensures that query without order by will have the result set sorted?
E.g. the query is
select * from table_t where odm_type='I' and odm_uid>nvl(OpUidParm,-1);
column odm_type has index created like this (default is ASC):
create index ODM_UID_I on table_t (ODM_UID);
Will such a query always return the first record having the minimal odm_uid in all Oracle versions?
Performance Tuning :: Index Usage In Order By Clause On Nullable Column
Jan 28, 2011I 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?
Creating Index On Hashed Column
Sep 23, 2010I currently have a 5 column index on a table with over 2 billion records (paritioned on created_date (weekly) that is not very effective.I am contemplating replacing this 5 key index and creating a new single column index made up by hashing of all the 5 five columns.
Is this a wise stratgey? How can I implement this so it is most effective and I dont shoot myself in the foot?
Creating A Multi Column Index
Jan 24, 2012I have in my database (OLTP-System) a table with about 6000000 records and a zise of about 2GB.
the way to create multi_column indexes on the table?
What are the rule to define the best-position of a column in an index?
index_1(col_1,Col_2,col_3) and not [ (col_1,Col_3,col_2) or (col_2,Col_3,col_1) or (col_2,Col_1,col_3) or (col_3,Col_2,col_1) or (col_3,Col_1,col_2) ] ?
SQL & PL/SQL :: Create Primary Key Without Creating Index?
Jul 12, 2012how to create a primary key with out creating an index?
View 10 Replies View RelatedPL/SQL :: Compute Statistics After Creating Index
May 15, 2013I have to create some indexes in a production database. Do I need to Compute Statistics after creating indexes? Or when I create they automatically are computed?
The version I'm using is:
Oracle Database 10g Release 10.2.0.5.0 - 64bit Production
PL/SQL Release 10.2.0.5.0 - Production
CORE 10.2.0.5.0 Production
TNS for 64-bit Windows: Version 10.2.0.5.0 - Production
NLSRTL Version 10.2.0.5.0 - Production
Store Data In CLOD Data Type - How To Create A Unique Index
May 20, 2013We have been recommended to store data in CLOD data type.
Sample data: 1:2:2000000:20000:4455:000099:444:099999:....etc it will grow to a large number.
We want to create a Unique index, for functional reason. Is it advised to create a unique index on a CLOB datatype?